Cables for a high-school newbie

Im on an extreemly tight budget. My goal for cables is simply to open up my current system, tighten the bass, and sharpen immaging, i dont want to color the sound at all (well, maybe a tad bit darker to counter the metal dome tweeters on my speakers). I have a sony cd player, Onkyo Tx 8211 reciever and a pair of NHT SB-3s (best speakers under $1k i've heard... and they're only $400 new if you shop around). are cables worth the dough at this level or not, and if so what brands should i be looking at? I need both interconnects and speaker cables. I listen to rock, small group jazz, metal (too bad metalheads can't figure out how to make a decent recording), and classical in that order.
thanks for the help