Choosing a video card and adding RAM

Ok I'm new here so sorry if I'm writing in the wrong place!
To the question at hand.
I own a PC with a AsRock 4Core1333-eSATA2 motherboard, and a power supply of 450 W.
So my question is would it be abble to run the Gigabyte ATI HD 6570 OC 1GB video card.
I'm looking to upgrade my pc with out spending too much money. And I'm thinking of adding 2 plates [FONT=Arial]Kingston DIMM DDR2 1 GB 800 MHz[/FONT] to the 2 that I already have.
I don't really have an idea of what I'm doing so I need some help.

Thank you!
I believe the 6500 series cards require at least a 500 Watt power supply so you will most likely require a power supply upgrade as well if you choose that card.
Also how much RAM in total are you planning on having? What processor are you running? And do you have a 64-bit or 32-bit operating system?
The minimum system requirement for the 6570 is 400 Watts so you should be ok with 450 depending on what else you have connected to the system.
Well I'm planing on having 4GB Ram since the motherboards max is at 4GB. And there are also 2 HDD plugged in, one is 250GB I think and the other one is 60GB.

Edit- the PC is running on Windows 7 32bit