I bought the Denon 1403 & JBL S38s as the beginning of a system for both music and HT. Right now I'm using it mainly for music (set to stereo mode, fronts large, no sub), but the bass sounds really flat. Does this receiver have enough power for these speakers without a sub? Any suggestions would be appreciated (i.e., what receiver to move up to, what sub might help fix this problem, etc.). Thanks.