SOUNDLAB ULTIMATE 545

@miko71 , This is true for the smaller speakers. The 8 foots speakers will make bass down to 40 Hz fine even at volume but subwoofers do better and using a high pass filter on the Sound Labs lowers distortion quite a bit by preventing the diaphragms from taking long excursions.
If you like rock and loud jazz IMHO subwoofers are mandatory but then again this is true of most dynamic speakers.

Pinotnoir, The only tube amps I would use on the Sound Labs are the Atma-Sphere MA1 or MA2. The MA2 seems to be a favorite. I have no heard one but Roger West relates many Sound Lab owners prefer this amp. They are vastly different to other tube amplifiers. They are also more powerful into the Sound Labs than their power ratings suggest. I think you can safely assume they are equivalent to a solid state amp of twice the power. Not every solid state amp will drive them well. I know for a fact the Parasound JC1 will drive them and I suspect other high powered class A amps will also. The JC1s sound more like a tube amp than a solid state amp. I am a huge John Curl fan.

@atmasphere , While technically true, high powered Solid state amps Like the JC1 do just fine to 105 dB (as high as I have gone) for several reasons. The JC1s due to a programming error I made absolutely fried the high frequency brilliance control and I mean barbequed BLACK and I had no idea this was happening until I smelled smoke. The JC1s merrily baked along without so much as a whimper. Tough amps. 
Next, while the Soundlabs are capable of making plenty of bass the long excursions required below 100 Hz doppler distort everything else the speaker does. I am of the firm belief, know it for an absolute fact, that full range ESLs sound even better, much better, if you use them with subwoofers. This cures the high impedance problem at low frequencies also. The 105 dB is without subwoofers. With subwoofers lord knows how loud you can go, certainly right past the threshold of pain. I would bet the subwoofers would be the limiting factor.
Having said all this there are quite a few Sound Labs owners who are convinced the MA 2 is the best amp to drive them. Hopefully, after I recover from dumping $50K into my system this year and the house renovation required by my wife (her part of the deal) I will be able to afford your amps and maybe a Dohmann Helix and a new Master Bath :-)
pinotnoir, The Antileon should be more than adequate for the time being. I would bet even better than most tube amplifiers with the exception of Ralph's amps. It is class A and 150 watt/ch. I bet it goes even higher in AB. However, next time around regardless of which amps you buy, get mono amps and place them right behind the speakers. This gives you the shortest speaker wires possible, a huge advantage with speakers that have low impedances. You should also run balanced cables to the amps. 

Pinotnoir, I have 645-8's, 8 foot tall 645s. Duke is correct about Atma-Sphere but as a rule they work much better with solid state amps. The problem for most tube amps is the extremely low impedance at high frequencies. This requires a LOT of current. Big solid state amps with over built output stages work best, particularly class A. The only exception I know of is the Atma-Sphere amps The two amps they have shown with are the Atmasphere either MA1 or MA 2, atmasphere would know, Ralph you out there? The other amp is the Parasound JC1 which is what I am using. But , I am debating getting MA2's and moving the JC1's to subwoofer duty. The JC 1+'s are about 1/2 the price of the MA2's. The efficiency of the 545's is just a little less than my speakers so you still need the power. Both amps get just as hot which is very so I hope you have AC.  I highly recommend you get a room control Preamp and two subwoofers down the line. You will increase your headroom at least 6 dB, lower distortion noticeably and you will be able to match the frequency response of the speakers/room perfectly. The result will be an outstanding image. I you go down this road give me a shout and we can talk about it.