Usher cp-6381, lacking in bass?


First I will roughly describe my system
Usher cp-6381 speakers
Krell s350 cd player
audio research ls2 preamp
krell kav250a power amp

My listening room is less than ideal I know but it is what it is. It is basicaly the sun room or Florida room and is made up of windows all the way round including back into the house, floor is ceramic tiled. Speakers sit on rugs on spikes on their cast iron bases about 12 feet apart and about 10 feet from my normal listening position.

I find the soundstage and voices to be impressive, however the lower bass is not, what is there is nice and tight but does not seem to go overly low. I also realise the amp is really a home theater amp hence the kav monicker but it was available and affordable...lol.

Room and layout cannot be changed for practical reasons at this stage so what might anybody more seasoned suggest to try and increase lower bass response and punch a little bit?
I mostly listen to hard rock both old and new.
Preamp? Power amp? CD Player, Speakers?
Any or all could be my concern, have had this setup like this for a good 2 years and am happy but just would like to take it to another level if possible without a second mortage!
Thank you

128x128uberwaltz
Guess I should have been a little clearer, not really looking to obtain subterranean bass levels down in the 25hz range or such, just more to flesh out the bass I have, maybe more punch and drive maybe better description?
Would like to not add subs, preamp does not have a sub out so would have to do with speaker wiring.

Subs help out with much more than low bass and could very well help do exactly what you're looking for along with possibly improving upper frequencies and overall soundstaging and imaging.  You don't need (or even want) a sub out -- that's more of a home theater thing.  Most subs will work with any line out from your preamp as well as at speaker level.  There are good companies that sell subs direct (i.e. SVS, Hsu among others) that offer generous in-home, low/no-risk trial periods and great customer support.  If you haven't heard what a good sub properly set up in a system can do, especially in your particular situation, I'd strongly suggest considering this.  Best of luck. 
Thank you Soix!
I honestly must say I had never considered a sub for my music rig. Guess I figured a well matched setup just did not need or want a sub?
And I do know just how well a good sub can work on the ht system, my ht rig cost even more than my music (have to keep the wife happy!) and it includes a REL Stentor 2 sub which will literally loosen your bowels on certain action movies...just as it is intended too.
But I had considered this to be a little unnatural and more a consequence of todays age where we expect action movies to involve us so deeply we "feel" the explosions as much as hear them.
Maybe I need to "borrow" it for a few days and see what effect it has....