SVI2004A
Synchro Bias
As for the SVI - based amps, I really think Technics had, and still has, a best kept secret to that design.
It's never been copied, and though pricey to replace when one goes bad, I've never heard a bad performing SVI amp.
My Technics SA-R277 receiver with the SVI3204 amp chip puts out a solid 60W per channel, and never seems to labor.
Of course, a little tweaking helps - cooling fan modifications, bigger filter caps in the power supply.
I highly recommend a V4X amp... It somehow flew under the radar. They're somewhat rare in USA... You'll know what I'm saying if ever you get one.
Masterdraco... A lot of the earlier SVI efforts had a lot more aplomb than any discrete amps in the same brackets. I personally have seen a lot of discretes sound like ass on difficult to drive speakers, whereas the SVI had no problems.

