Audio Research VT80SE amp vs Prima Luna EVO 400 or 300

How do you find the newer ref 6se / 160s compare to ref 40 / 75se ?

I agree with @jjss49 about the sound signatures of both amps.

One thing to consider is the VT80 SE comes with KT150 power tubes, the PL with EL34’s. The PL can also use KT150’s with the flick of a switch.
Using KT150 change the PL from romantic to more dynamic with more bass and treble extension.
That is my experience with the PL Dialogue Premium HP (basically same as Evo 400 minus the balanced connections). Don’t get me wrong the PL DP HP is dynamic, holographic and has great bass and treble extension, there is just more of it with KT150.
The PL will allow you to experiment with several power tubes:
EL34 (and it’s equivalents), KT77, KT88, KT120, KT150.

The AR can use KT120 or KT150

Both the AR and the PL feature auto bias for the power tubes.

Maybe the flexibility of having the option to use several different model power tubes is important to you.
Maybe point to point wiring instead circuit boards is more important to you, as the PL features.
PL also runs the power tubes easier for longer life.

Either way, two great choices.
I would consider what the speakers sound signature is and chose the amp that compliments them.

Ex. Accurate with metal dome or diamond tweeters pick the PL.
Warmer, slightly rolled off sounding
go with the AR.

Thanks to all for your helpful posts.

@rushfan, both my golden-eared wife and I are partial to "warm." Hence our fondness for the vintage Sonus Faber GH speakers, although I’d never characterize the sound as "syrupy."
@5751That "hum" issue is a concern. I’ve had to deal with that in the past and it can be maddening. Have you tried a cheater plug on the amp power cord?

I test drove the PL dialogue premium against the Evo 400. There is clear sonic improvement, specifically in the detail and transparency.

How much will close the gap to the ARC gear?
Only one way to find out. As a brand, ARC is better. But the PL sounds meaty and ballsy like nothing I've heard before. Euphonic is the perfect word.

It is dead reliable. Every potential pain point in owning tubes is slain. Personally, I prefer detail to warmth...but what I'm stuck with is pretty damn good.

I have the Evo 400 power amp fed by a Don Sachs Model 2. Great combo.

Flame — hard to say.  Different rooms and very different speakers.  Some time ago when I replaced the 75SE with the 160S, in the same room and system, paired with DAWs, the 160S brought dynamics and “jump factor" to a whole new level.  It is dynamic as hell.  Spanish Moon from Waiting for Columbus became a thrilling ride; air drumming is an involuntary (if mildly embarrassing) response.  The 160S also brought a different sense of clarity/definition.  I hesitate to say better, but different.  More forward.  If you get off on the arresting transparency of a perfect Julie London or Nat Cole recording, or you want to feel the breathiness of Ben Webster, I’ve heard nothing better.  But I think in 10-20 years some will still love the 75SE for its ability to remain unnoticed, its naturalness, and its relaxed presentation.  In real life, when someone is playing a piano or guitar in your room, they are not trying to impress you with sonic charms.  Such is the sound of the 75SE.  In fact, it is VERY good in this regard.  But a true confession: I waffle between my teenage brain seeking punch and sizzle, to a more adult appetite for effortlessness and flow.  For example, at least once a month I seriously consider auditioning a D’Agostino stereo amp in place of the 75SE.  The 160S also offers more punch, with a noticeable "charm" in that lovely lower midrange, upper bass region.  And good ole’ bass is definitely tighter and more pronounced.  Final word on all this: the ARC break-in period is notoriously long, and it’s not malarkey.  Make sure you’re listening to a fully broken-in ARC amp, otherwise all bets are off.