Both Classe' + Bryston are sonic matches for B&W loudspeakers.
Most importantly, which brand(s) of cables/power cords are you planning to use?

mkingston:

Looking purely at specs, you are making a serious change from a well respected multi-chaneel (5.1 in this case) amp to well regarded mono blocks.

Do you still need 5.1? If so, you'll need 5 Brystons and one hell of a pre-amp. Just an obvious point in case it has been overlooked. I am saying 5 Brystons because the Classé cranks out 300 watts/channel. Not sure if you have all 802's or different speakers for surround and center... or are converting to two channel. At around $9,000 for the latest revision of the Classé, and around $5,000 for the Brystons, it is rather odd how they work out to actually be nearly identical in price if you are moving to two channel. If you are moving up to 5.1 with needing the Brystons, of course price will increase considerably; as well as power and rack space. Just things to keep in mind.

I will say the Brystons will provide a lot more power; and the 802's can handle up to 500W vs. the Classé's 300 per channel. So if it's more power you are after and perhaps more separation, the Brystons may be your best bet. I am assuming under $25,000 where budget is concerned; and you prefer the power of solid state over tube.

Just for thoroughness of response, some other contenders in this price range:

1. Bob Carver Crimson/Raven 350 Tube monoblocks @$9,000 for a pair
2. Mark Levinson No 351H 350 Watt mono block Note: Levinson carries a nice variety of dual-channel, 3-channel, and 5-channel amps; a little north of everything else....but you may prefer the sound.
3. Pass Labs 350.5 350Watt x2 Stereo Amplifier @$11,500

Respectfully,

Ron

I am using the Musical Fidelity M6PRX amplifier to drive my Vandersteen Treos, which are rather power-hungry.

I have yet to hear any amplifier for under $10k that sounds as good.

It sounds WAY better than the Bryston it replaced.

You will also note that it is one of the few amps that are rated Class A and cost under $10K.

IMO it is a real bargain at only $3500.

All:

I agree the Musical Fidelity is an excellent piece of hardware; however, in this case, the B&W 802's are engineered to fill a large room (rated at 500 watts).
I am also assuming that's one of the reasons the OP suggested the Brystons. They are no slouch either and also make exceptional equipment and in this case, are significantly more powerful than the 300 Watt Classé he wishes to replace.

Respectfully,

Ron

The B & W 802 is rated at 90 db per watt by the manufacturer. Driving them with 500 watts of power would probably damage them, as that calculates to an SPL of around 116 db, which I doubt that they can produce without speaker damage.

90 db/watt is anything but power-hungry; rather sensitive and efficient, actually, for a speaker of that type and size.

When John Atkinson tested the Treo speakers, he determined that their sensitivity was 82.5 db/watt, which is very low.

The 7.5 db difference means that the Treos will require 5 to 6 times as much power for the same sound level as the 802 speakers, and I can assure you from extensive listening experience that the M6PRX amplifier can drive them to any level that ears can stand without distortion. At 4 ohms, it can put out well over 300 watts per channel.

The M6PRX unquestionably can put out far more power than the 802 speakers can ever use. 100 watts of power will drive them to 110 db, which is very very loud. Any amplifier with more than 100 watts per channel is really more than you need, and would have the potential to damage them if you are not careful.

I was providing my recommendations based on specs as well as my experience with the CM line of Bowers & Wilkins, room theory and SPL calculations, planning, and mostly the OP's dissatisfaction with an already well regarded 300 Watt amplifier.

The relevant specs of the Vandersteen Treos (also very respectable speakers) are:
Recommended Amplification 40-160 watts per channel into 8 ohms
Sensitivity 85 dB, 1 meter/2.83 volt input

And the Bowers & Wilkins 802's
Recommended amplifier power 8Ω (minimum 3.5Ω)
50W - 500W into 8Ω on unclipped programme
Sensitivity: 90dB

The Vandersteen Treos are indeed fairly difficult to drive at 85dB ... Though they suggest 40-160 watts.@8 ohm. I would hazard to guess doubling that with a 4 ohm load is what has been assumed and I concur.

So having quoted specs, I may move on to calculation. As I wish not to re-invent the wheel, I've located a suitable online calculator and intuitively arrived at a peak SPL of 102.6 dB for the Vandersteen's when seated 15 feet away. Driven at 300 Watts; and allowing for some room gain. I think this makes sense so I will use the very same calculator for the B&W's. To quote apples with apples, the Treos output -6dB when at 30ft (approx 10 meters); or a respectable 96.6dB in a large room.

Typically manufacturer sensitivities are usually quoted at 1 meter from the speaker. Noting that SPL drops 6dB per doubled distance, the B&W max recommended wattage is again within rationale based largely on this distance rule. For example, if one is seated 10 meters from the speakers which are designed to drive larger rooms, utilizing a 500 Watt amp, and allowing for room gain, the PEAK SPL would be 103dB. 10 meters sounds very far; but think of the scenario of a house party with several quests, located in a great room; and certainly "off-axis"...then these measurements fall back into reality. Further, amplifiers are not run at their maximum dial value of "10", so to allow for that, the levels would no doubt be lower and within Rock Music comfort; or around 95-100dB PEAK. One can again certainly turn the volume DOWN, but there is no "11" if one purchases inadequately powered amplifiers. When specifying an amplifier, I would imagine it to be the very rare occasion to have a client complain of too much power. And in conclusion, B&W wouldn't advertise wattages that would cause damage to their own product.

I also learned some interesting things reverse engineering this calculator when plugging in various room loads, speaker placements, and distances in order to arrive at your 110dB calculation for 100 Watts driving the 802's. I mathematically conclude you are either placing your speakers 10 feet from the listening position in a well loaded room and well placed speakers; or are placing them even closer and maximally leveraging the room acoustics as many audiophiles typically do, based on arriving at a value of 110dB for a 100Watt amp driving the B&W's.

Again, I would hazard to guess the OP is either using a larger room; yielding greater distances for speaker placement; or has other concerns I do not at the moment have enough information to pose any other calculation; other than an intuitive hunch he is displeased with a 300 watt high-end amplifier.