Advice on purchasing classics amplifiers.Which one

Beware of possible repairs lurking beneath the surface, esp. the transformers [as my VTLs required]. The VT is the easy choice if a modern design and execution is a parameter. But the 6550 is not the ideal output tube. Also avoid the Mk III bs, for which ARC is so famous. You'd think they'd get it right the first time. If I may, why the fealty to tubes? Good luck and let us know how you make out.

Jaguar1845, I would say that while the VTL amplifiers of 1980's vintage are not normally thought of as being unreliable, the build quality racheted up by leaps and bounds during the 1990's. Compare an amp of theirs from 1990 to one from 1996; night and day different.

For example, check out some of the circuit boards in some(not sure about this one) of their amps from this period. They are secured at one end, with a lot of parts on the other. It's a classic diving board effect, with the board flapping around when handled. It was corrected as time went by, and VTL products appear to offer great build quality. Also, the quality of wiring, soldering, and just everything in general related to the amplifier improved steadily for the better as new models and revisions were released.

In no way do I mean that this amplifier will not be reliable, but I have a friend who owned some VTL products, and always commented on how things had improved over the years from so - so to very, very good.

Based on that, my recommedation would go to either the Audio Research or the Conrad Johnson. Both are normally bulletproof. Which you decide on should come down to your taste, as these amps are very different in sound.

The Audio Research will not at all feature a classic tube sound. Rather, it will be fast, analytical, dry, and pretty neutral. In other words, it will sound much more like the Krell and Mark Levinson amps it is meant to compete with.

Conversely, the Conrad Johnson products of the 1980's are classic tube. They will be sunny, warm, and romantic. If you are looking for tube sound, it will definitely be the CJ. Bass will be more loose than the AR, and the treble will be more restrained.

I know which I would pick, but your decision can only be made by you.

ps - Based on your list of amps/price range/vintage, I would also look around for a VAC amplifier. Excellent quality stuff, with sound that really special. I have really liked my encounters with the Vintage Hi - Power amp.
GOOD LUCK!

I need an amplifier that could produce the bass slam that the Monolith II are noted for, coupled with a fine mid range and highs. I play Jazz, rock and R&B music. This should help in your advice. I cannot stand to listen to an amplifier that does not have the bass slam, but must also perform on the rest of the audio range.
Also the AR VT-100Mk2 at 100 wpc, I believe is not enough for CD's with extended low frequency music. Back to the topic, and with the information I have provided which would you recommend? Again thanks to mall for your iformative suggestions. Audiogon is truly a great place.

...looks like you definitely need either sub or >=200W/ch amp even tube.

First, try to get the price down for VTLs.
Be ready for surprises using 14y.o. equipment or the dealer check-up and replacement of old aged parts is highly recommended in this case to avoid more serious troubles.
In general VTLs built like a tank and never break but to ensure yourself you shouldn't take chances.

Forget about used 15y.o. CJ that can bring too much "surprises"

Another great option you might research especially for jazz and R&B is Jole Electra VAMP integrated hybrid amplifier with MOSFET output that could even cost bellow 2k used and has extra preamp outs for bi-amplification if needed.

If bass is a priority you might want to consider one of the newer sweet solid state designs like the CJ MF series, Gamut or Plinius. Reliable and within your price range.