one of the best sounding recordings i have heard on this forum was using the HD500 4CM through a 5150 III. Will never forget that recording, and it was blind - he faked the entire thread into thinking it was some other setup.
If i were worried about hauling cabinets, a 5150 III 50 watter, HD500, and a 2x12 of choice would be the best setup for bang for the buck. full MIDI, excellent effects, killer cleans from the HD500, and external loop on the HD500 - best of all worlds in terms of versatility without compromise.