For $1000 you could *easily* get a good system. You could get a complete tower for ~$850. With the parts you've already got, it'll be no problem at all.
Where abouts in Aus are you? Check if you're close to an MSY store, they've got pretty good prices: Locate US
Tassie, so the limitations start there unless I buy online.
@ keshialee, please don't double post, if you have something else to add to the conversation and no one has posted a reply since your last post (within a 24 hr. period), please use the edit button (looks like a pencil) to add it to your previous post.
You might be able to rig up an auxillary power supply but this one fits in a 5.25" bay.
Newegg.com - FSP Group Booster X5 450W Independent/Supplementary SLI Certified CrossFire Ready Active PFC Dedicated Multi.GPU Power
Sorry about that, I have been doing that a lot.
As for that link, am I right in assuming that is an external thing? I'm really trying hard to keep up here, but I struggling a little. Am I right in thinking that something like that supports my current PSU?