fogia.4: I have no long term experience with the MPX3 and SA5000 combo (only heard at meets, where the combination sounded terrific), but decided to post anyhow. Mainly because as an early adopter of the SA5K's (read: bought for $700 from AudioCubes before they became available in the states - ouch!
), I am still a big fan of their sound.
I
have had a SinglePower Maestro, and have listened extensively to the PPX3, MPX3, Maestro, and SDS (Mikhail builds great amps), so feel a slight qualification to contribute.
Bottom line - I expect a MPX3 + SA5000 would be a wonderful combination. Any good tube amp I have heard (so far this would include EarMax Pro, MPX3, SinglePower Slam, RS Raptor) has sounded just terrific with the SA5K's. Something synergistic going on with that incredible detail and speed of the SA5000's and the analog continuosly variable output of well implemented tubes.
Yes, the speed, detail, and energy of the SA5000's with a nice tube amp is quite special. Excuse me while I go fire up my little EMP and indulge ...