I'm slowly upgrading a pioneer HTIB 510. I replaced the L/R w/rt25i's, then replaced the center w/a sony n495. What a difference! but I could really tell that it didn't match the polk's so I returned it and got the csi30 and love it. Everything flows so much better. However, I've notice that it seems to annoyingly thump with deep voices. I haven't had a chance to play w/it too much but it almost seems more noticeable w/low volume. I have the receiver set to small speakers and crossover at 150, tried 100 and 200 and not much difference. I'm even wondering if it's simply the sub turned up too high. I love my polk speakers and wonder if I just need to tune it in a bit. Also, any ideas on which (economical) sub to match everything with?