Hi, this is my first post. I am struggling to trying to get the clarity and volume that I want out of my Mp3s from itunes on my laptop (Mac Powerbook G4). I was wondering what is the best way to get more umph! I am a college student living in a "party frat" so loud clear music is essential I live for really loud music.
My current setup is:

Receiver: Sony STRDE197 (good receiver?)
Speakers: Two polk audio RTi4s and two sony ss-B3000 (to add some bass)
The hook up: I have my stereo hooked directly to my computer through my computers headphone jack.

Right Now I get decent volume, but i can tell something is lacking from my system. I want some more Umph, and clarity. What is the best way to do this?

Would I want to buy a preamp to put between my computer and stereo?

Do I want to buy a whole new reciever?

Or should I buy a computer peripheral like an external soundcard that runs through my USB or firewire port?

I am merely a poor college student so I cannot get too expensive, but I am willing to pay for good sound. Your opinions are greatly appreciated (espeacially by my neighbors ).

Thank you for taking the time,
Will