Sony ES receivers are not good at driving difficult loads and any Martin Logan is at least fairly difficult. Will it "work?" Certainly, but you won't hear nearly all of the quality those speakers have to offer. You could hook up an external amp to the preamp output of the Sony ES as a temporary solution. Just so you know that I speaking from practical, hands on experience I worked for Martin Logan dealers for 3 years and have owned a pair for 10 years.

High quality, affordable amps that are fairly prevalent on the used market include; but are not limited to:

Adcom
Rotel
Parasound

100 to 200 watts should do it. I can here your question, "But isn't my Sony 100 watts?" Yes it isn't that simple.

The wattage rating method used for audio products isn't standardized. The only way that wattage can be used in comparing two products is when dealing with models from the same manufacturer. Is a 300 watt Bryston twice as powerful as the 150 watt Bryston? Yes it is. Is a 300 watt amp from "X" twice as powerful as a 150 watt amp from "Y? " It might be, but it's far from certain. This is because of the variables in rating wattage. Below are just a few:

1. The Impedance used to load the amplifier's outputs during testing, rated in Ohms.
2. The frequency range being driven. Some manufacturers drive 20Hz to 20,000Hz because that is what many accept to be the human hearing range. Some cheap receivers are driven at only ONE frequency, 1kHz being the norm.
3. How many channels are driven AT THE SAME time. Just because a receiver or amp has 5 or7 channels doesn't mean that they were all driven during the test. Nearly all receivers only drive one channel during testing.
4. How long was the test. Many times an amplifiers circuit can deliver very high wattage but the power supply and heat sinks won't allow it to continue doing so for long.
5. How much "Total Harmonic Distortion" was deemed acceptable during the testing. More distortion allowed means more watts on paper but distortion is also usually the cause of damage to speakers.

For mass market goods the wattage is largely determined by the marketing department and then the engineering department does the algebra to figure out which variables need to be manipulated to give them the desired answer. The Federal Trade Commission's major requirement is that the rating method be disclosed to the public.

When dealing with multi-channel receivers the mass-manufacturers play one more game. The units are described as 100 watts X 7 channels. Do they mean that the receiver will put out 100 watts into 7 channels AT THE SAME TIME? No, most of them mean that it is capable of putting out 100 watt into any one of the channels with little to no power going to the other channels.

As an ESL owner I can say ML's are speakers I could live with.
Don't leave out Audiogon in your search for a good used amp. It's by and for audiophiles. The selection of products is aimed at someone who would buy ML speakers and other high end gear. I have more confidence purchasing from Audiogon than e-pray.
With that said, what kind of budget are you working with for an amp?
If you want/need something quickly you could try an Adcom GFA-555. They are very reasonably priced and will drive just about any load imaginable. If you don't like it you can quickly and easily sell it for no loss.

BTW: You may find that Klipsch speakers will not be a good match for ML's. Speakers used in a 5.1 system should be timbre matched. The ML sound is quite different from anything Klipsch makes. The Klipsch sub is another question mark. Of course, only your own ears can and should decide.

I would also consider an Emotiva XPA-2 to power your ML mains. If you don't like it, you can return it for a full purchase price refund after 30 days.
http://emotiva.com/xpa2.shtm
http://www.affordableaudio.org/EmotivaXPA2.pdf

The advice here has been so good, I only wanted to post to agree with what you've already been told!

Solid home runs from those guys!

I bought a used Adcom 5802 on Ebay, sent it to THESE folks who did a great job reconditioning and upgrading ( no mods). Their price for services is very reasonable IMHO but you must factor in shipping costs both ways which can be a little pricey on such a heavy item.

Still, for under a $1,000.00 I have a reconditioned /updated 450W @ 4ohm amp that effortlessly drives my ML

RG has a very good recommendation there. I owned an Adcom GFA 5802 for many, many year and it work well with my Logans; which are an order of magnitude more inefficient than yours. It's also a Nelson Pass design. He's a very famous and well regarded designer (Threshold and Pass Labs being his most famous ventures.) His stuff is usually a ton more expensive than what you can pick up a used 5802 for these days.

By the way have you figured out what the budget is for the prospective amp?

Quote:
How about a rotel RKB-650

That's a whole home amp designed for running in wall speakers for background music options. That really wouldn't be an appropriate match.

Given your ? re the Rotel and the centre speaker purchase it seems that Home theatre is important for you.
Is this the case?
How do you divide your listening in % between HT and stereo?
Is HT quality up there with your stereo needs?

Reason I ask is that I run a HT in my system but 95% of my quality is in the Mains for stereo.

Important to nail where your priorities are if you have a limited budget....still $1,000 after centre purchase?

Quote:
Pete,
I would say 60% stereo and 40% HT. BTW I am watching a Parasound 7100 and 5125 as coupled units......these must be the ticket right?

I dunno'. It depends on who's playing and what you want to hear.
Seriously, this site is mainly for music enthusiasts. Although many of us have an HT system of one type or another it is usually accorded second fiddle.
If you have to compromise and use one system for music and HT get the music part right first. It's much easier and far more effective sound wise to add surround and MC capabilities to a good two channel system than vice versa.
I've heard some very good two channel music systems that sound very good when surround and MC is added. Sadly, in my experience most surround based systems don't do all that well when playing two channel music.