Interesting question. I've tried sub/small speaker vs full range speakers a few times and was never impressed with the sub (crossover artifacts seem to outweigh ability to go lower) but in hindsight I think the room was always getting in the way.
+1 for regular vs HP speakers, seems to be a bit more of a bass-heavy tilt in the HP speakers and trying to figure out if I would like that or not. That said, will end up pulling the trigger on some M60HPs to find out myself eventually...
EDIT -- off topic but &^$&^%$!!, missed some nice B-stock natural cherry M3v4's.