I run a P4 2.26 and a ti4600 and I find that once my subd models get particularly complex everything does noticeably go on a bit of a go slow. So I normally make the basic shape in polys, convert to subds at level 0, reconvert and then do a lot in polys (going back to subds now and then to see how it looks). I find that way I can work a bit more precisely without things chugging along. Then I do some tidying in subds. Not sure if this is the proper way to do things but it works for me.

Nice feet btw. 8)