For your purpose, there are no better amps than the ones made by InnerSound to drive the type of capacitive/resistive nightmare that your Acoustats represent. It ain't tubes, but since you're using a tube preamp, it will almost sound like a tube amp. It will handle the load with ease and allow the Acoustats to open up and do their stuff. Most "tube" amps on the market won't even come close.
Although I'm not very experienced with tube equipment, I am aware that an OTL type amp may be the only tube-type design that can drive a load of that nature. The OTL designs use no output transformer, but instead have a cathode follower output tube so that they can drive lower-impedance loads with better stability & coupling. Joule Electra builds such a design; no doubt there are others as well.
Also refer to this thread "tube amp for a difficult load":
I think you need to decide if you like Tubes or your existing speakers better. Because for $1500 used, you are not going to find a tube amp that can drive those speakers well. Especially when compared to a $1500 SS amp.
With more of a budget, I would suggest the ARC VT100 amp ($2500 or so used). This tube amp could drive the speakers pretty well.
Personally, in that price range, I would look at Monarchy solid state gear. The Monarchy SE100 Deluxes and the SE100 amps are great amps and sound a lot like tubes due to their Mosfet outputs.
A step up from Monarchy is Plinius SA100 mk3. This amp can be had used for $2200 (which is a virtual steal). Plinius is a world class amp that can only get better if you get two of them and go MONO.
Anyway, if you like tubes better than your speakers, I would suggest getting new speakers. If you like your speakers more, get a musical solid state amp like the Monarchy or Plinius gear, and I think you will be quite amazed.
This advice and a cup of coffee nets you a cup of coffee.
Plato, Bob, and Keith,
Thanks for the quick response and information. There is no such thing as bad information and I appreciate it all; that's the only way to learn. I will research your recommendations and see if I can't improve things. Also, I was just reading on the Apogee forum page, that some one was using a Crown Micro amp. I know these amps have a pretty noisy fan, but they are suppose to deliver over 500 watts at 8 ohms and drive down to 2 ohms pretty easy. I just wonder about the quality of the sound.
$1500 is really cutting off the kind of tube amp you need...around 100 watts per channel. The Sonic Frontiers Power 2 would be a good choice but they're going for around $2000 used, maybe a little less. You might also want to investigate an outboard auto-transformer which is essentially an impedance multiplier to make that difficult load more manageble. You find them here:http://www.condor-connection.org/asog/tweaks/ps/zero/index.html
Good luck...I think tubes and 'stats are the way to go, but you must be careful.
For a tubie sounding amp that can drive your Acoustat44,the Belles 350 is a good canditate. It is 250 watts per and very well built. The price is somewhere around $3500.00. This will also match your quicksilver tube pre-amp.
I have never heard the Crown amp. Personally, I am not all that fond of amps with fans... just one more thing that can break... and if it does, who knows how much damage can be done from overheating (if you are not there when the fan breaks)?
You might want to consider Rogue amps. They are close to your price range used. But I still think it will be difficult to effectively drive those speakers with a tube amp in this price range.
Rogue 120''s or a good deal on a Mesa Baron like I got.The Baron lists for $4K but can be had fopr $1500 used.150 watts full pentode and the abiltiy to tailor 12 5881's/El34's in thirds to triod/pentode make this the best piece of gear I have picked up.
The pre-map you got is a pretty fast sounding tube pre-amplifier, if you like fast music, you can match a transitor amp without any problem, but if you like classical music and slow type of music, then you surely need a tube power amplifier. But in the market, there seems to be no tube power amplifier with 2ohm output impedance selection. Fortunately, I know one manufacturer can give you the 2ohm output option, it is the "Space-Tech Lab" , the web site address is "www.space-tech-lab.com". Those model VP-102 and VP-103 output transformer have 2/4/8 ohm wiring point, although the standard model is come with 4/8 ohm , but you can ask for internal wiring of 2/4 ohm output without extra cost. The price is really reasonable, just about $1500 new with all point to point hand-wired, no printed circuit board. Take a look and you might find something really interest.
Thanks everyone for the all the inputs. Well, I wasn't able to find a tube amp that would really do what is need at a budget price. So I ended up buying a Carver Lightstar Reference. While I can still still send this amp in soft clipping, it sounds great. The Acoustat produced bass that I didn't know they were capable of. I have never been a Carver fan, but I must say, they beat the heck out of my Adcom 656 mono-blocks. The sound field is a little in the rear, but very open. I may need to try another preamp. I will try this setup for a while until I find something better, is possible.