Amp recommendations

ML's are nice speakers. You are going through the proper route, in my opinion. Thankfully, BestBuys didn't sell you anything else.
McIntosh is also wonderful, but pricey. You can do just as well with more moderately priced equipment. Being a Vandersteen man, I am not the best source of information regarding powering Martin Logan's.
Your speakers are rated 20-500wpc-quite a range. I would opt for something in the 150-250 wpc range.
You could easily find a used McCormack amp and preamp, like the DNA-1/RLD-1 preamp. SMc Audio still upgrades their older models-I'm getting my DNA-1's converted to monoblocks, as we speak.
Perhaps an Ayre AX-5 integrated- though only 125 wpc.
I post these as food for thought. Other will be posting soon, and hopefully have more direct experience with your speakers.
Bob

Hello Chuck,

Martin Logan / McIntosh owner here. FYI, Martin Logan / McIntosh are known to synergize well together (work very well with each other). I have the Vantage speaker paired with an MA6500 Solid State Integrated amp, both a step down or two from the equipment you mention. I have not heard the 13A yet but hope to soon. Personally I like the Martin Logan / McIntosh pairing very much, but do prefer SS or solid state over tubes with the Mc gear. With my gear, this combo provided excellent top to bottom frequency response and with the tone controls on the Mc, you can, as I do, adjust to fit your room quite easily. Some frown on tone controls, but I value them very much. I think many do though they may not step up and say so. At any rate, when the tone controls, or parametric EQ are at the 12 o'clock position, they are out of the circuit.

Martin Logan ESL speakers are known to require a lot of power and amperage. This is because they dip to around 1 Ohm in the upper frequency range and some amps don't like that. So be cautious and make sure whatever amp you consider can provide solid power and will be stable at 1 Ohm as well. 

I had to have some lights replaced on my Mc a number of years ago and so I had another integrated doing duty while the Mc was out for repairs. It was really not contest at all. The Mc was much better being much more open and holographic; the overall sound was just much more pleasing. The stand-in amp if I remember correctly was an Anthem integrated. It drove the speakers, but it did not make music. So, with that, what ever integrated you buy, be sure to get a dealer demo in your house so you can be sure you'll be happy.

Finally, I know you have a budget around $5k. But I'd consider the MA7900 or the MA8000, here's why. I've had my MA6500 for around ten years and I'd really to take a step or two up and this is what probably either one of my suggestions would do for you over something around $5k. You have a really nice pair of speakers. They can only shine as good as the upstream equipment is.

Maybe you could call and talk to Ron Cornelius at McIntosh. He demo's all the gear at all the audio shows and can tell you what you would get for your money. Very nice guy and he'll shoot straight with you too.

Also, go to the the Martin Logan Owners Club website. You may find some information of value there. http://www.martinloganowners.com/forum/

Hope you have fun in your journey.

Congratulations.

There are so many good options at the 5K mark and under.

Here are a couple.

There are some Hegel H360  listed for the low 3K used.

The Lyngdorf TDAI 2170 is very current and multifunctional.

Keep checking Audio Classics website. Currently there’s a couple of Mc. integrateds listed.

http://www.audioclassics.com/

You just spent $15,000 for speakers. You shouldn’t go cheap with the electronics. Pass Labs is a brand you might take a look at!
http://store.acousticsounds.com/d/119195/Pass_Labs-INT-60_60W_Class_AB_Integrated-Integrated_Amplifi...