To what extent do you think this advice could be applied to a Conductor 3 Performance?
I've never tried the Performance, so I can only speak from testing on other amps. I've tried all of my op amps on the C3R, Playmate 2, and other smaller portable amps. The op amps always have the same sound signature; the op amps don't differ their signature or technical abilities based on the amp they are in. So I feel comfortable in saying that regardless of the amp the Sparkos SS2590 is the most accurate op amp out there, with the Sonic Imagery 992/994's being a very close second. Third place is pretty far off from #1 and #2 , and there are several op amps around that level. That said, my opinion for 3rd is the Burson V6 Vivid in both accuracy and enjoyment.
As mentioned over the last few pages the SI 992 & SS2590's should work great for almost all setups. It's a very balanced sound. It is possible to push the resolution of the sound a bit further by using 4x SS2590's instead, but whether or not that will be better than the 992+SS2590 setup will depend on your entire audio chain. All that said the SS2590 & SI 992/994's require more space than the V6 Vivids, so it all comes down to just picking the best op amps that will fit in the case.