Your amp will do a good job of driving speakers rated at a nominal 4 ohms. Its spec indicates it delivers a relatively high current level. The amp/speaker pairing should be fine.

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A dealer told me over the phone that there is no advantage in driving a 4 ohm speaker. Will someone please clarify this for me.

The dealer didn't clarify? You didn't ask?

There are no real advantages to driving a four Ohm speaker rather than an 8 or 16 Ohm speaker. In fact, there are many possible disadvantages to driving a four Ohm speaker.

Why don't you read this thread; http://forum.stereophile.com/forum/showf...true#Post23814. It should explain a fair amount regarding impedance and speaker loads.

One problem with the dealer's apparent advice is it is too simplistic. I assume this dealer was trying to sell you something other than your first choice.

You (and the dealer) are quoting the "nominal impedance" of the speaker as stated by the manufacturer. As you'll see in the linked article and in many of the measurements done in Sterophile, the manufacturer's spec doesn't always mean much in the real world. Most importantly, saying a speaker is four Ohm or eight Ohm ignores the real world situation of a wandering (dynamic) impedance curve as frequency changes.

Look at a few measurements done by Stereophile and you'll see the actual impedance of a speaker covers a wide range of impedance loads depending on frequency. So, you can reasonably say no speaker is "four" or "eight" Ohms. That is just a convenient number the manufacturer can place on a spec sheet.

Moreover, the electrical phase angle of the speaker load must be taken into consideration. Phase and impedance taken together at any frequency represent the real load the amplifier must drive.

Phase angle in a speaker is created primarily by the crossover components used in multidriver (two, three or more way) speakers. You will see phase angle measured in every recent Stereophile full speaker review. If the phase angle is very capacitive it will have a largely negative phase angle. If the phase angle is stated to be positive going, the speaker load is primarily inductive. In either case, as the speaker moves from 0 phase angle to a high phase angle the speaker moves from being a resitive load to a reactive load.

Amplifiers prefer to run into a resistive load.

Asking the amplifier to drive a more reactive load will typically ask the amplifier to deliver more current and/or it will alter the amplifier's frequency response and damping factor. This is a broad statement and the linked article should explain how to look at speaker measurements and determine which speaker will be difficult or easy to drive.

The article will also cover back EMF, which is a situation for which there is no specific measurement taken since this will vary with the amplifier driving the speaker. Finally, the sensitivity of the speaker will be addressed in the article. All of these factors should be weighed before asking an amplifier to drive a difficult load.

Fortunately, in your case, the Rowland is up to the challenge of all but the most power hungry, difficult speakers on the market. If the Rowland sound and the Rainmakers suit your taste, the amplifier should not be your main concern. Rowland paired with Totem is not exactly my cup of tea. For me there might be possible better matches for the Rowland - which I think is excellent gear by any estimation. However, I would suggest you either bring your amplifier into the dealer's showroom for an audition, or preferrably ask for a week's audition in your own home before you make a final committment to buy the Totems. I might have very different tastes than you and you might very well find the Totems to be a perfect match for your electronics and music. No matter what, I don't think you should be concerned about the amplfiier's ability to drive most "four Ohm" loads.

You get my admiration, Jan, for your willingness to provide chapter and verse. When I read the question, I just threw up my hands and decided to cut to the finale. What an interesting combination, a man with both that amp and that question. Who'd a thunk it?

Who'd a is correct.

Nice Job, Jan.

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I believe you double your wattage with every 3 db increase in speaker sensitivity.

A 3db increase in power does equal an increase of twice as much power measured in watts, but don't get caught up in watts into 8 or 4 ohm speakers and speaker sensitivity.
If watts are good then a 4 ohm speaker would be better than an 8 ohm speaker. And a 2 ohm speaker would be even better than a 4 ohm speaker. And then a 0 ohm dead short would produce the most power and be best. High sensitivity in a speaker does provide more volume for a given amount of drive. But is more volume your goal or is quality of sound important too? The big picture. The big picture.
I was thinking of selling my ProAc's and getting the more efficient B&W 804s.

I really wish things were so simple.
Yes, a speaker with a higher sensitivity will produce a higher sound level than one with a lower sensitivity.
But that doesn't have anything to do with quality of sound.
Possibly even a louder more efficent speaker will produce more distortion than a less efficent speaker being driven with more power. It's always something. Sorry.