I want to upgrade my graphics card, but I've only got $300 to spend, which includes buying a new power supply, since mine is currently 300W. Any suggestions as to how I should go about doing this?

I got lots... but a whole lot of questions too.

What are you doing that requires a better gpu?

How much room is in your case? You have a pre-built system, and as such limits your choices.

I'd recommend a Antec or a Corsair, seasonic, silverstone, all at or Around 550 to 650W tops.
A modular style will give you more room in the case.

The case isn't particularly large. I'm planning on using the new card for gaming purposes.

PSU: Corsair 650tx $92
Corsair TX650 V2 650W ATX 12V Single Rail 53A 24PIN ATX Power Supply Active PFC 80PLUS Bronze - DirectCanada
or $79
Antec Earthwatts Green 650W Power Supply ATX12V V2.2 EPS12V Active PFC 80PLUS 120MM Fan - DirectCanada

GPU: $171
XFX Radeon HD 6850 775MHZ 1GB 4.0GHZ GDDR5 2xDVI Display Port HDMI PCI-E Dual Fan Video Card - DirectCanada

The problem is your case, You'll need to measure your case to double check the gpu slot.

I choose directcanada to save you the pst. Thought as youre in BC, you could be near a ncix store and not have to wait.

I looked at ncix and theres some good deals there too. but that is basically what you want, though I'd suggst looking nto a case upgrade too.

Thanks, I'll look into that.

*I think I saw a Radeon HD 6870 for $173 though.

Very possible, just watch itsnot after a MIR. I never buy stuff if i need the rebate to fit my budget.

Also watch for card size.

Hes canadian,m we get shafted.