Like any preamp pedal yes of course it can be. Just need to turn off the IR section as I mentioned before.
I would put it in the FX return because I think it would sound better. I don’t like any preamp pedal - regardless of what model it is - in to the front of an amp.
I have had once since the Rig Talk JVM buy in of 2007. It isn’t a sexy forum cred amp but it easily competes with amps much higher in price. Fantastic amp.
Also a massive 5150 212 combo fan here. Easily the best out of the OG 5150 series. But I got a Stealth EL34 100 watt recently and when I biased it up properly that amp came alive. Sounds insanely good.
Having owned both and played them extensively, the EL34 version is definitely smoother and a little looser. They were going for a more vintage flavor. I think it is cool that it isn't just the same amp with different power tubes. There are actual design differences between the two. Not massive...