I had the same problem with my densen-spica angelus setup (some recordings sound very thin to the point where I avoid listening despite liking the music). I ended up with a Rel strata subwoofer. This has worked really well for me : the good recordings are now amazing, and the bad ones are enjoyable. There are, however, still a few recordings which are not helped by the REL, maybe because it's upper frequency roll off is set at 30Hz, and the source material simply doesn't go down there. There are a very few discs that are not improved and no discs that are worse with the REL. I consider it a great buy.
Also, several years ago I had a friend with a Quad stup. Quad has some wierd tone controls which are supposed to "cause less distortion". I remember playing with them (I think they're called lift and tilt) and I was very impressed ... it seemed like quad had got it just right. It gave a small lift to the bass or treble, but not in the artificial way of a traditional tone control. However I believe that my Densen amp is more detailed than the Quad, for about the same price, so maybe less is more !? If this hobby were easy it wouldn't be so much fun !
So what did you end up doing ?