Advice on purchasing classics amplifiers.Which one

Hard to know what you like or what your system needs to sound the way you want it to. Depends on what you want to get out of your system - how you want your system to sound etc...Totally your call. Good luck!

I would probably agree with Fefer 77 and say VTL. However the ARC is an extremely good amp and very stable.

My guess is the ARC is a bit less of the classic tube sound if that helps your decision. You did not say what direction you wanted to take your ML's.

Try to find an Audio Research D 250 mk. II, it is a lot better. Actually one of the best ever made by ARC and it has really got a lot of power.

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!