Need new power supply; tight on money

Hello, I currently have a Bluestar 680 Watt power supply that I have been told time and time again to ditch and upgrade. I had bought it about a year ago when my previous power supply was killed by my current Graphics card (I didn't really pay attention to the more fine details that go into computers then) and needed something to get back on and do homework and what not. While I know the risks of having a cheep power supply, I never had the money to upgrade it to something that was... safer. It has done me well for the time being (my system doesn't really pull much power at the moment, so it isn't being stressed much), but, i am upgrading my Video card and CPU very soon and I fear for my system's safety.

Basically, I am upgrading from an AMD Phenom II X3 710 to an AMD Phenom II X4 960T BE (which I am hoping to unlock and/or overclock) and a Sapphire (I believe that is the brand) ATI Radeon HD 4850 to a Gigabyte Nvidia GTX 560 Ti. Together they are going to cost me about $300 before rebate, and that really drains my pockets. I'm just looking for a Power Supply strong and reliable enough to power my system for as little cost as possible. Whether is it modular or not really doesn't matter to me; I just want to spend as little money as possible.

System Specs (after upgrades):
BIOSTAR A870U3 AM3 ATX AMD Motherboard
G.SKILL Ripjaws X Series 8GB (2 x 4GB) DDR3 1600
Gigabyte Nvidia GTX 560 Ti
AMD Phenom II X4 960T BE

Also, any advice or articles you can share with me to help me convince my dad that my cheap power supply isn't the best thing to have would be fantastic. He hasn't ever ran into problems with power supplies in the past (they have only (rarely) failed on him after some time), so he doesn't really see the necessity of the regulations and safeties that are always recommended. I really would like to have him on "my side" when I make the purchase.

I'm also hoping to place the order by tomorrow on Newegg, so, if I can get any and all advice before then, that would be great.