Cardio, Boys, Cardio . . .
Right now, you'll probably have to go with anything that fits. But as far as getting your ass in shape, cardio is the way to do it. Forget the treadmill, and go straight for a stairclimber - it will strangthen your leg muscles (a little icing on the cake in terms of what you've been doing with weights) and help reduce your butt. Second choice - an eliptical crosstrainer at a high incline (like the Precor, since Startracs and Life elipticals do not have adjustable inclines).
By the way, has anyone had the same problem with shirts (as in dress shirts or cotton shirts with collars)? I have a 19" neck, but if I try to buy a shirt with a 19" neck it fits me like a freakin' tent. (Most athletic-cut shirts only go up to 17" or 18" necks.) It seems that on-the-rack shirts that fit at the neck/chest balloon out at the waist big time. A major drag, the only solution to which is getting them custom made. Not to mention being tall and trying to find shirts with 37" sleeves . . .