Best buy had this onsale for 25% off, and I got an extra 10 % bringing the price down from 500 to under 350 bucks. I couldn't resist!

I brought it home and hooked it up to my Onkyo reciever. The question I have is on the hook up. Right now I am going from my receiver out and branching into a Y cable and going into both the Dedicated line-level/LFE RCA inputs. What exactly is each input and how should I be hooking this up?

All in all I like the sub, but it sure doesnt rumble like a 400 watt sub should in my eyes. It is very mellow for music and I usually turn it up to 7-8 (out of 10) for steady bass. I also boost the sub output a few db on the onkyo receiver. It sounds best for movies, some scenes it shakes the house, others you can't tell it is there. Any suggestions?

The connection sounds ok, did you check both the manual for the sub and the manual for the receiver?

You will need to calibrate your system with a setup disc and preferably an SPL meter.

As for the quality of the content you would need to have another sub for comparison although some dvds have great LFE tracks and others don't.

what does LFE stand for?

LFE - Low Frequency Effects

You might do better, posting these questions on the Klipsch forum

http://forums.klipsch.com/idealbb/default.asp