I agree Don that the XA.8s draw more from the wall than the XA.5s. I think it is 50% for the series (300 Watts vs 450 Watts draw). Your point is evident from the heat generated. I've never had the XA.5 more than lukewarm whereas the XA.8 get relatively hot to the touch if left on for extended periods of time. Mind you that I'm in Chicago and it's still early March so the house is generally cold.
I think a bit of the current draw is mitigated by the power less than 1W stand-by draw. With that said, I'm not sure what the XA.5s drawn in stand-by mode.
As for colder/more neutral, it's close. The XA100.5 seemed a bit more romantic. The XA60.5 had a sparkle that the XA100.5 seemed to lack. The XA100.8 seemed to me and in my particular system a step closer to the XA60.5. Vocalists a step more forward. Bass more powerful. Blacker, blacks.
With that said, two points. First, I decided to trade in the XA100.5s for the XA100.8; thus, some bias (in taste and buyer's honeymoon period). Second, the XA100.5 were very good. Different. By a hair the XA100.5 were better than XA60.5 in my system. A by a hair, the XA100.8 were better than the XA100.5s in my system. And in all fairness, I may not have traded them if I hadn't still be in the trade-in period allowing for no depreciation to factor in and received a very reasonable price on the new model.
Listening to Bob Dylan's Nashville Skyline right now, it is difficult to ignore the music and think about upgrades. ...it's time to flip slides. Good night.