Help Me out here!

ok guys i have a motherboard: Gigabyte GA-M55SLI-S4 and desktop tower already, i would like to know what power supply, GPU and also Processor, would be best for gaming and most recommended. i have a low budget so dont be pullin up some $1000 gpu's LOL, the most ill spend on all is $300 us dollars.

Edit: Don't be saying its a shitty motherboard or soo cuz i work with what i have atm.

You're not going to be able to upgrade a GPU or CPU with that motherboard, it's just not happening.

What I could muster up for $300:

AMD Phenom II X4 965 Black Edition
ASUS M5A78L-M LX PLUS AM3+
CORSAIR Builder Series CX430 430W
100357-2GL Radeon HD 7750 2GB

Total: $289.96 w/ PSU rebate (Rebate is $10)

You'll probably need to (what I mean is you'll definitely need/have to) upgrade your RAM too if your motherboard is that old.

G.SKILL Ripjaws X Series 4GB (2 x 2GB)
Total: $319.95 w/ PSU rebate

or
G.SKILL Ripjaws X Series 8GB (2 x 4GB)
Total: $339.95 w/ PSU rebate

It supports socket AM3+, the CPU is AM3 but it's backwards compatible, it also supports CPU wattage up to 125, the CPU takes 125 watts.
ASUS - - ASUS M5A78L-M LX PLUS

The GPU is PCI-Express 3.0, but will work in a 2.0 slots, just not as fast as it could.

Also, there are two other 7750s you could buy, this Gigabyte one or this MSI one. They're the same cards essentially but I personally like the style of the MSI one the most.

About the RAM I suggested, AMD says their AM3 socket Phenom II CPUs support DDR3-1333 - "Support for unregistered DIMMs up to PC2 8500(DDR2-1066MHz) and PC3 10600 (DDR3-1333MHz) – AM3"

You'll need to overclock your RAM to achieve the 1600 speed with that motherboard, and correct me if I'm wrong but the CPU too. My mistake,
G.SKILL Ripjaws X Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333
or
G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1333.

You could even also look into getting a FX series CPU from AMD. Though I kind of uh... don't recommend it.

@zachair