I need help upgrading my system

My current system is in the mid to low quality range. ATM I mainly use it for listening to music (primarily metal and rock; I'm young, I know) and A little for gameing, But i mostly use my headphones for that. Heres what I currently have:

Insignia Is-HC040917
-totaly pos
-designed for surround sound
-says "500 wats" (I doubt it)
BBE 362 Sonic Maximizer
-bbe process and bass contour turned all the way up
1 Realistic Optimus T-110
-original 6" woofer exchanged with 8" woofer
-have annother, not using it
-used as "center" channel
2 Fisher DS-825 l/r
2 Yamaha NS-A636

I got the speakers for free and the reciever for cheep, so for a grand total of $65, its not too bad. However, I think its time to upgrade. Also remember that all of the sound is comming from my computer, and all songs are encoded in either aac or apple lossless. That being said, I want a new reviever/amp, and 2 new speakers to replace everything. What I need to know is what should I keep, ditch, upgrade, etc. However, I am also how on cash, so I need really cheep, but really good sounding with Slipknot coming out of my good sound card encoded in acc. What can I do?

thanks in advance!

Thanks for the help, Flrnlamb. I'm gonna go with the cheapest denon. Do I need one with Audyssey? And if so, which one is the cheapest with it?

What does Dappolito mean?

Any other recomendations with the fact that I'll be listening to metal and gaming w/ them in mind? And also price is a big factor too.

Thanks for the help so far everyone!

Also, I'd rather not have a sub, so what speakers would be efficient, be good with metal and games, have active bass, and be fairly cheap (used)?
Active woofers? Well, years back, Home Theater Magazine did a $3k system face off" between 3 of the writers. The one that won the challenge used some then current Boston Acoustics powered mini tower speakers, which used some 8" active woofers, driven by a Jolida 40watt/ch tube integrated amp!! The same system looped in a simple DD Yamaha AV receiver for movie dubties, and processing DD/DTS sources. This system won because of the excellent mating between the more refined sounding tube amplifier, and the efficient dynamic clear sound of the semi active speakers.
Well I know Definitive Technology made a similar type of speaker that retailed for $500 ea, or $1000/pr, range. They, I believe, were the BP2006tl's. These, while not Dappolito (woofer-over tweeter-over woofer), still offer quite strong dynamics, and a clear, workable sound, similar to the sound of the Bostons - which sound better with tubes. Mated with some little tube integrated amp, you would have an excellent sound, with pretty darn good dynamics for rock! It's a thought. Of course, then were talking no system EQ here - which, in your tiny room, would be a HUGE benefit, indeed.
Since your room is so tiny, you will DEFINITELY need the benefit of the newer Audyssey technology! So, you could jump on one of the Denon AVR-688's or 1708's on ebay for around $285-300 range, and mate them with similar speakers I described. Then, you might even look into finding some innexpensive tube integrated or amp to mate up with em down the line - which you could then loop the Denon into for movies. I think it's a thought.
Other route is to go with some high efficiency Klipsch RF-5's(?), with the same Denon combo - maybe trying the tube amp in the system, down the line.
It's going to be hard to keep a low budget, and still get you full range speakers, room eq, and quality sound! You go with certain combo's, and then you need more amplifier, separates amps, more expensive speakers, and so on...so it's tough.
Actually, your challenge here, for a cheap budget, with great dyanmic sound,and quality overall sound, is the floor standing speakers, sans the sub! I could get better quality in some nice bookshelves, adding a great deal on some little 8" or 10" sub
hope tis heps...