Are all of these parts compatible

And also, does anyone have any idea what kind of frame-rates i'd get on Quake Live? I realize it isn't a graphically intense game, but since I play it competitively and am on a budget, I need to get the best framerates for the money.

I just need to know if the parts are compatible, I have picked out which parts I want. The "How to ask for new build advice" is mainly about what parts and where you want to buy them from. I already have chosen the parts, I would just like advice as to if they are compatible.

Yes, the components are compatible. What I'm trying to say is that some of your choices aren't that great. If you posted in the correct format then we could help optimize your build. First off, that 500GB WD drive uses two 250GB platters. The new single 500GB platter drives are considerably faster.

SAMSUNG Spinpoint F3 HD502HJ 500GB 7200 RPM 16MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive $54.99

The Antec Basiq PSU's aren't very good. I would have a look at the Antec EA-500 or Corsair 450VX PSU's for a single GPU setup. The motherboard you picked supports crossfire. Are you wanting to leave crossfire open as an option? If so, you should be looking at a quality 650W PSU.

What resolution does your monitor run at? I didn't ask you to post in the correct format for fun. It's pointless to recommend a GPU without knowing what resolution you'll be gaming at. you might want to check out the new ATI HD 5750 and 5770 GPU's. Again, I don't know your budget or anything so I can't really offer much advice.

Here's a Crossfire ready build around your budget. I included a DVD burner which puts it just over budget. I noticed you didn't include one, so I'm not sure if you need it.

Antec Three Hundred Black Steel ATX Mid Tower Computer Case - Retail
http://www.newegg.com/Product/Prod [...] 6811129042

Antec EarthWatts EA650 650W Continuous Power ATX12V Ver.2.2 / EPS12V version 2.91 SLI Certified CrossFire Ready 80 PLUS Certified Active PFC Power Supply
http://www.newegg.com/Product/Prod [...] 6817371015

http://www.newegg.com/Product/Comb [...] mbo.285167 $109.94 (Case + PSU combo)

AMD Phenom II X3 720 2.8GHz 3 x 512KB L2 Cache 6MB L3 Cache Socket AM3 95W Triple-Core Black Processor - Retail
http://www.newegg.com/Product/Prod [...] 6819103649

GIGABYTE GA-MA790GPT-UD3H AM3 AMD 790GX HDMI ATX AMD Motherboard - Retail
http://www.newegg.com/Product/Prod [...] 6813128398

http://www.newegg.com/Product/Comb [...] mbo.291508 $218.99 - $15.00 MIR (CPU + motherboard combo)

SAMSUNG Spinpoint F3 HD502HJ 500GB 7200 RPM 16MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive - OEM
http://www.newegg.com/Product/Prod [...] F3%20500GB $54.99

SAPPHIRE 100284L Radeon HD 5750 1GB 128-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card - Retail
http://www.newegg.com/Product/Prod [...] 6814102859

OCZ Platinum 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10666) Desktop Memory Model OCZ3P1333LV4GK - Retail
http://www.newegg.com/Product/Prod [...] 6820227478

http://www.newegg.com/Product/Comb [...] mbo.280049 $227.98 - $10.00 MIR (GPU + RAM combo)

SAMSUNG Black 22X DVD+R 8X DVD+RW 16X DVD-ROM 48X CD-ROM 2MB Cache SATA CD/DVD Burner - OEM
http://www.newegg.com/Product/Prod [...] 6827151192 $29.99

Total - $641.89 - $25.00 MIR's

You could knock $12 off the build if you use your original CPU choice in this combo:

http://www.newegg.com/Product/Comb [...] mbo.291456

I really like the Phenom II X3 720, though.

You also never said where you're planning on buying components. I'm not sure if you live in the US so you have access to Newegg or not. That's one of the things included in the "How to ask for new build advice" sticky.