mf612 OP Amp to Pair with Revel F228be
Quite a hard load on amplifiers, have to be a good one to get the very best out of them.
Stereophile’s Revel F228be measurements
"The impedance magnitude remains below 8 ohms for the entire midrange and bass, with minimum values of 3.42 ohms at 98Hz and 3.55 ohms at 290Hz (fig.1). There is also a demanding combination of 5 ohms magnitude and 39.5° electrical phase angle at 390Hz. While its nominal impedance is specified as 8 ohms, the Performa F228Be would work best with an amplifier that’s comfortable driving 4 ohm loads."
This would be very nice integrated for them, if he’s still got it for sale
https://www.audiogon.com/listings/lisa8830-gryphon-diablo-120-solid-state?refsource=hifishark
Or if you've got the bucks, it's bigger bother.
https://www.usaudiomart.com/details/649572544-the-gryphon-diablo-300-mint-condition/
Cheers George