CAT JL-3 Versus VAC phi 300.1 monos?

I don't know much about the CAT amp, (other than Ken Stevens is a great designer, and his equipment sounds incredible!), but I have auditioned the VAC Phi 300, (configured as a stereo amp), at a friends house. It was a great amp, with incredible treble response, (the best I've ever heard actually), and a lovely mid-range, especially for vocals. (The bass was very good, especially so for a tube amp, although we both felt that the Lamm M2.2 (220 wpc hybrid) monoblocks were better.) I can highly recommend it. And running them as monoblocks will help the bass response, from what I have read.

One thing I will bring up, is that the VAC amp does run fairly hot. And running two of them will certainly raise the temperature in the room several degrees unless you have air conditioning. (Other than this slight annoyance, these are great amps, and certainly are reference quality.)

Good Luck in making a difficult choice!

The CAT will make the VAC seem like an air conditioner:)

OP, have you heard either?

First response was spot on, both world class amps and you would likely be delighted with either.

I have lived happily with a pair of 300.1's for a couple years now so I can share that in my system and to my ears, they are beautiful....

From hearing the CAT amps at 10 years of CES shows and owning the 300.1 also owned CAT REF Preamp, my feelings are the Vac amps are a little more musical not tuby while the cat amps to me sound a little cooler in nature. I feel the Cat amps sound little faster and more solid state in the bass, but this also gives it a little cooler sound in general. Both great amps that will also depend on speakers and other sources used.