You'll probably hear a wide range of inputs but my personal experience with my older Aerius i model ESLs is the more clean power they get the better they'll sound, especially their bass response. I drive mine with a pair of vintage McIntosh MC2200 amplifiers and they sound good to my ears. I occasionally switch to my other amplifier which is a Vincent SP-331 (150wpc/300wpc) and I prefer the MC2200. I have also tried several other borrowed amplifiers from friends ranging from Parasound, Conrad Johnson, Prima Luna, and Bryston and with the exception of the Bryston, I still preferred the sound of my old McIntosh amplifiers. The Brystons were the 7B-ST monoblocks and what impressed me the most was the incredible bass I heard from the Aerius which I did not think was possible from their 8" woofers. Some folks have had good luck with class D amplifiers which may be easier to find within your budget, even new. Whatever you decide to get make sure it can handle 4 ohm load with ease. Generally, amplifiers that double their power as the load is halved tend to have good drive for demanding speakers like ML ESL. If you're fixed on getting something new, one option might be the Schiit Vidar with 200wpc at 4 ohms.
Hope this helped.
As usual a big +1 for @gdnrbob! Steve and Co. are upgrading my DNA-1 as I write this. The last time I had it upgraded was 16 years ago. It has sounded great since then, but Steve plans to do very extensive upgrading as much has been learned and tech. has improved over the years. I can't wait to hear music through it once it returns. If you would go that route, Steve will want to know about your system details to be sure his modifications are geared to optimize your system performance. This is SMc Audio's site address: http://smcaudio.com/ Good luck!
I would look at the Hegel H80 Integrated...someone is selling one here for $950. It's 75wpc is capable of driving those ESL's (91db). The Hegel is very well reviewed. Also, someone is selling a Classe CA-100 $899 This is a stereo amplifier only it needs a preamp but for $899 its a great sounding stereo amplifier that will drive those ESL's np.
In the price range you are looking at. Without going vintage which can be hit or miss. I have noticed some used Rotel amplifiers on Ebay that might work for you. The RB-1080 is nice but can be bright. Class A/B 200 wpc. at 8ohm and built like a tank. If you have a little patience I’ve seen them go for $300.
But since you said "60/40 movies with your surround system", There have been a few Rotel RMB-1575’s available at your price point. And having 6ohm ESL speakers that will drop to 4ohm’s at times I read. They might be a nice fit. Five channels "All driven", rated 250/500 wpc at 8/4ohm should give you power and detail enough. And an easy load for the amp to run. And then you could upgrade the power to your center and surrounds as well with the remaining three channels.
When I listen to the ESL’s they do sound pretty darn nice with the NAD 368, 80 Watts $895 w/o media streaming card), though better with the 388. https://nadelectronics.com/product/c-368-hybrid-digital-dac-amplifier/
If you haven’t listened to Rogue Audio out of Pennsylvania, their Sphinx would drive the ESL’s very nicely (no DAC, but has headphone amp & phono preamp & can work with theater by setting volume but that’s another thread). THEIR MARKETING IS VERY VERY BASIC LOOKING BY THE WAY, so ignore that. The Cronus Magnum II (out of your price range which is $2500 absolutely blows alway the ESL’s. Even blows away the ESL 9’s, and 11’s too :)
The Sphinx is hybrid integrated, 100 WPC, at $ 1500. Also has outputs for Subs.
Thank you all so much for your advice. I have been a lurker on here for a while now trying to learn as much as I can and have noticed how knowledgable everyone seems to be. I plan on using the Pre outs on my Yamaha 2050 atm until I can get dedicated seperates. I am even considering selling 1 of my dynamo 700's and use those funds to up my spending on a good power amp. My hope would be the two 8 inch woofers in the ESL's would produce enough bass to compensate for the loss experienced with going down to 1 dynamo.
http://https//www.ebay.com/usr/orlous5 I have purchased from this guy several times. He stands by everything he sells. messaged him and he said he had several amps an pre' set he could offer you at your price point. He garantee's everything that he sells. Most of the gear he sells isn't on ebay though. But he lists it as people ask.
And sells through Ebay.