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
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....
How best would I connect a sub to my system?
I use balanced interconnects between preamp and power amp
could i just use the regular rca outs from my preamp that are unused right now?
Uber, I found out that my room has what is called a "bass null" at pretty much the only place I can put the sofa.  When I stand at the back or sides of the room, the bass goes really deep and strong, but not when seated on the sofa.  It has to do with the geometry of the room, and there is not much I can do about it, as, like you, I'm not really wanting to do the sub thing.
Hey MTROT, that is very interesting as I thought that if I stood in the middle of the room that bass was slightly improved but as you say the rooms are what they are.
As I have a rel stentor 2 sub in my ht rig, I am going to give it a try, when I can summon up the enthusiasm to move 110lb of dead weight from there to my music room that is..........
Make sure the guy with the sub has a good return policy.  Heh heh. 

I'm no sub expert, but REL seems to favor speaker level output to their subs if you can do it.  I read a review of your sub where the reviewer preferred it that way for music duties.  Anyway, you'll want to experiment with the crossover and volume to get it to disappear and blend seamlessly with your speakers.  Great speakers BTW.  Always liked Ushers.  Best of luck and keep us posted.  Remember, lift with your legs.