experience with Threshold SA/2e or S/500 amps?

I use a slightly modified S/500 Series II. I would describe it as very dynamic, open and neutral, but, not necssarily warm. The S/series are class A/AB, the first 20% of their power running in class A into an 8 Ohm rating. The pure class A SA Thresholds are reputed to be warmer and more recesssed. I'm confident that any of the Threshold's with enough power for your room and listening levels can "control" your speakers. The SA and Series II amps are reputed to be more stable than the ealier versions. The factory e series provides for true balanced (upgraded versions have XLR in-puts, but aren't truly balanced) twin trannies, and are DC coupled. The e series are said to have tighter bass, but, the earlier single ended amps are said to have a sweeter top end.
I'm not familiar with your speakers, other than they are not particularly easy to drive with their 4 Ohm, 85dB rating. The S series will double down, but as they do so you may expect their level of class A opeation to halve. If you prioritise warmth; go with the class A SA/ amps. If you prioritise power; go with the higher powered class A/AB S/ series. The higher the power of the S/ series the more base class A you'll get. Perhaps the S/450e might be worth consideration. The older the amps, the more likely they may be need of a tune up with perhaps some new caps. Jon Soderberg of Vintage Amp Repair can be relied on to do this correctly.

Funny that this thread popped up again. I been recently thinking about it. Perhaps, the extended frequency range caused me to dismiss the warmth aspect of the S/500 Series II. In retrospect it does have a touch of warmth. Regarding the proper load, most Threshold's are recommended for loads above 4 Ohms. That said, they are tested into loads below that and probably shouldn't have much difficulty with lower impedances.

Thanks for the follow up, It's always nice to know where these things end up. Good luck with the Classe'.