Michael's (richeydog's) point about the difference in room size is a good one. It could very well account for the lack of "punch" you are experiencing. I have the M60s with a HSU STF-2 sub in a 2500 cubic foot room, 1500 cubic feet smaller than your current room. No lack of "punch" here.
I, too, am curious as to why you don't want a sub. I don't think you are aware of what you are missing (were missing, with the other setup) without a sub in the mix. It's perfectly OK that you don't want one, but I'd just like to understand why not.
