Hey Ian, like you I'm also a student. I've got a 2.1 system that cost about $2000 to build, which I realize is about double what you want to spend, but there are a few inexpensive components in the system which are worth you're consideration.
First of all, I'm using an Emotiva XDA-1 DAC, which is really an awesome piece of gear and only costs $300 (occasionally marked on sale for $250). See this thread where it competes admirably against a DAC that costs more than ten times that amount! (http://www.hometheatershack.com/foru...a-xda-1-a.html
) If you plan to play digital content, the quality of your DAC is really important. The DAC that is built into your mp3 player or your computer is pretty poor compared to most any separate DAC that's on the market, and you'll hear a big difference in the detail of your music once you bypass your computer's built-in DAC and use a separate. (There are 4 ways to do this that I know of -- (1) if your DAC has a USB or Firewire input, connect the DAC to the computer using a USB or Firewire cable; (2) if your computer has a mini-optical out, as current Macs do, run a mini-optical to optical cable; (3) if neither, get a soundcard that has an optical or digital coax out; get an Apple Airport Express and play your music wirelessly, discussed below.)
Second, I've listened to several budget high performance subs, and in my opinion Outlaw offers the cheapest that can still compete against the big boys. One of the previous posters mentioned the Rythmik F12, which is is actually the sub that I'd like to upgrade to eventually once I've saved up the money, but if you're trying to make every dollar count, I'd say pick a sub from Outlaw's lineup that meets your budget. Although they aren't quite is musically pristine as Rythmik, they still sound really good playing both music and movies, and they have plenty of power. Dr Hsu (the designer of Hsu subs) has consulted for Outlaw, so several of their subs bare a marked resemblance to Hsu subs. I agree with a previous poster that I don't think you are getting your money's worth with JBL. Not that JBL subs are bad -- far from it -- but you are paying for a name brand.
Third, if you'd like the ability to play content wirelessly, such as from a smartphone or a laptop, the Apple Airport Express has become hugely popular with audio enthusiasts. It is a wifi router/network extender that also has the ability to provide transport for digital content via a mini-optical port using. It outputs a 16 bit / 44.1 khz PCM signal, so as long as you have the Airport Express hooked up to your DAC with a mini-optical to optical cable, you can play digital music over your home wifi network using "Airplay", and the sound quality is as good as if you were playing music from your computer using a soundcard with an optical out. The two drawbacks are (1) bit rate / sample rate are limited to 16/44.1, so you can't use it to play hi-res music, and (2) it requires that you use iTunes to play your music, although Apple has made the Airplay spec available to developers, so its possible that there are 3rd party applications that are Airplay-compatible that I'm not aware of. You can find an Airport Express for $60-80 on eBay, or $99 from an Apple Store.
Lastly, a previous poster also mentioned Audiogon. I agree that this is definitely a good place to pick up used gear for a reasonable price. They have several policies in place to protect both buyer and seller, and they have features that allow you to negotiate with sellers.