What would be considered Tops in Digital Amps?

One of the issues that I previously hadn't taken into account for upgrading my pre/amps was the issue of power consumption that Class A amps cause vs. a digital amp. From comparison tables I've seen produced on AA operational cost of Class A amp could be in the up to $1000-$1500 range, whereas digital amp can "cost" in power consumption about $100-$250 annually.

With these ongoing "cost of operation" issues for amplification power, what would be considered TOPS in the digital amp series (Bel Canto, PS Audio, etc) for close to equivalent sound quality to the best of Class A amps?

Lastly, with using digital amps, does that make a big difference in the type of preamp that a person would have to consider?
I think "the best" is a question too system dependent to answer without equivocation. You'll find proponents of Bel Canto & PS Audio, each singing their praises. The PS has been a revalation in my system, very good synergy with my Magneplanars. The question about preamp matching is very relevant in my experience with this amp. I am using a Music Reference RM5III that has variable gain. The systems' transparency, lack of grain, etc. is much better at the very lowest amount of gain possible, which is 3.5 db. Higher amounts of gain degrade things very noticeably. The input sensitivity of the HCA-2 is higher than average. However, the factory is happy to build an amp for you with lower sensitivity suitable for a given preamp with higher gain. If you are fond of passive preamps, this is a great amp for that route. Remember, if you order from the PS Audio factory, you get a trial period.
Photon, I must say your post was one of the best and most informative,I've read. You covered a lot of ground. Excellent!!
FYI, Electronic Visionary Systems is introducing a digital amp in the near future.

I have never heard a digital amp in a system I am familiar with.