Well, the Megaverb uses the TC-5000 algorithems, though I think it uses the TC-2000 tails. The Classic verb is more of a Lexicon, less shimmery, bigger, fatter, warmer. The Powercore card is running the algorithems on 4 Motorola 56K DSP's, the same ones your likely to find under the hood of a lot of hardware processors, so it should, and does sound fabulous. To tell the truth, I haven't touched the M-One since I got the PowerCore, though I was going to fire it up last night as I was auditioning verbs for a track. Now that the thrill has worn off a little and I can be more objective, I'll try to do a comparison this weekend. I have no doubt though that the Powercore will win just based on a one to one reverb comparison. One thing that needs no comparison though is the fact that an M-One will give you one stereo reverb, but the Powercore will give you eight, or 4 and a bunch of other stuff: EQ's, compressors, limiters, delays, synths, a TC Finalizer, the new 247c limiter (an 1176 clone), etc.
Cheers, RD