bel canto and wyred 4 sound

I don't think you can compare the two brands. Wyred amps are mostly similar save power ratings however BC designs vary more. THe better BCs have improved power supplies and are tube pre-amp friendly. Different BCs use different version ICEPOWER modlues. The Wyreds are tube pre-amp friendly but do nothing special with teh power supply TTBOMK and I think all Wyreds use the same version of the ICEPOWER module. So you have to compare specif models, not brands in general.

Resale prices tend to be good relative indicators of how specific models compare feature wise I think

The ASP module includes powersupply. So, they are pretty much plug /play.

The ASC module is meant to be powered from an ASP module OR from a stand-alone PS. At that point you can buy a transformer and a capacitor bank, or go SMPS.

The output sections are very similar...topology and device selection.

It would appear that W4S uses unmodified ASP modules with perhaps a few changes on the input end. My PSAudio, built in the same facility has what they call the 'GainCell' on the input. I have no detail on that, except it is a potted module.

Other 'd' implementations may have character of their own. Hypex, Spectron and the little known International Rectifier are all 'd' entries. Spectron is proprietary, Channel Islands uses Hypex and I have no idea about IR modules, except I've got one out in the garage needing a power supply.

The 2 major topologies of 'd' amps, what are called 'FullBridge' and 'HalfBridge' may account for differences in sound.

Magfan, aside from adding an input buffer, I know for a fact W4S does modify their modules.

Would you or anyone consider such changes making the ASP moduled amps an Apples / Oranges proposition or maybe like a Fuji /Gala? (I'm a BIG fan of Apples!)

Changing (upgrade?) some caps? The only thing that would have a major effect, IMO, would be to change the feedback loop gain. I doubt even changing parts in the Zobel would have a major effect. The W4S integrated also has a different input impedance than the 'stock' ASP module OR my PSAudio which is a near-dead ringer. That supports your 'input buffer' remark.

I'd love to know what changes W4S makes. IF they are THAT major, why aren't they trumpeting it to the sky?

I'd LOVE it if someone organized a 'd' amp shootout. If it were local enough, I'd even bring my GCC250 over and put that in the rotation.

Fuji/Gala... :D

Yes, caps are changed in a couple of locations.

I'd love to be present for a Class D comparison too. Off the top of my head, the only others I've heard were Bel Canto's TOTL monos. They sounded good too, but were in a different rig/room so not really much of a comparison.