I have added Infinity speakers and that did improve the sound but I think I would like more, both quality and volume. I've been told it is simple enough to add an amp and the new speakers would be able to handle the more power. So I see amps for sale between 60 and 160 bucks. Any suggestions for what I need? 2 channel or 4 channel, I'm lost? This has got to be a budget upgrade not a new total system. Thoughts welcome.