Get the Antec Earthwatts, it's one of the best budget powersupplies out. Read reviews over the net, they are generally very positive. Jonny guru's review http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=35, either the 430 or 500 should suffice.
Your Z-5500 has a dac ready in it so that is useless. Reason the sound card is important is for DDL which implements surround sound (5.1) in games and movies through SPDIF instead of using 3 analog plugs to get it.
I love the sound quality of my AC-1.
My headphones sound SOO much richer than before and it feels like I'm at a live performance. I also get no more annoying buzz that I had with my realtek onboard when there is no outbound sound.
After reading your post I downloaded a tone generator and tested out the frequency myself. The subwoofer receives sounds up to 150hz while the speakers receive sound all the way down to 120hz. :confused:
I still believe that this system would benefit greatly by replacing to speakers with bigger...
Actually the z-5500 crossover is set at 120hz.
I really wish they had adjustable crossovers which would make this system 129381293x better.
Different speakers will definitely improve the highs and mids. I tried out few different car speakers, out of curosity, with the z-5500 before...
I have the same set and I would love to try http://shop3.frys.com/product/4005092;jsessionid=QvsihDBKBzM9hKzpUzD-FA**.node1?site=sr:SEARCH:MAIN_RSLT_PG
since its going for very cheap right now.
My old Nforce 2 soundstorm couldn't push these at all.
The onboard soundcard I have now can actually push these and remove distortion and rattling, which I found odd.