I actually by a small margin preferred the TC-750 or TC-754 with the TC-754's external SMPS (it looks like a bigger unit compared to the TC-750's SMPS) over the Schiit Mani.

The Mani is well extended in both bass and treble, has great control, good slam, but ultimately sounded less clear and flatter. The TC-750 with the TC-754 PS wasn't as well extended in the bass, but was marginally clearer and definitely more lively if not a bit more grainy. With the Sigma-11, the TC-750 just sort snapped into place and ran away from the Mani with the huge dynamics, increased resolution, refinement and poise. Obviously this comparison is not fair since a commissioned AMB Sigma-11 is about $350 more.

It does make sense though. The TC-750 is all discrete with no opamps. There appears plenty of room for improvement. I believe there are two input and two output caps, both electrolytics. There is cap sound; and stock, I though it sounded a bit grainy. I did parallel the output caps of my TC-750 with tiny 0.1uF WIMAs. Might be interesting completely replacing all of those 'lytics with poly / film caps. They are small values, so it should be doable.

Finally, the TC-754 does sound a bit warmer than the TC-750, and tiny tiny bit more veiled - probably from the multiple input switching circuitry.

P.S. I'm putting together a shunt PS from a kit and a SOLA power supply on the cheap from eBay. Don't laugh. Both of these were considerably better sounding than the Sigma 11 on the BW. There's no guarantee it will be the same with the TC-750, but they are worth a try since effort will be minimal.