Would like to upgrade graphics and memory....

Hello everyone:
New to the board here. I have a question with regard to improving speed and graphics.
I have the following hardware:

ASUSTeK Computer INC Model A7V8X-X acpi bios Mother board.

L1 D- Cache 64 KB 2-way set associative, 64-byte line size.
L2 l-Cache 64 KB 2-way set associative, 64-byte line size.
L2 Cache 256 KB 16- way set associative, 64-byte line size.

Memory DDR 1536 MBytes. Dram frequency 132.7 MHz. ( 3 slots @ 512 MB each).

I use windows xp and have road runner internet.

I'd like to increase speed and performance. I do a lot of web surfing, play games on facebook, etc.


I'd like the facebook games to play and load faster.
Would a dedicated graphics card help and can I put one on this system?
Also thinking of upgrading the memory. I have 3 slots as indicated above. I seem to run out of memory and my browser freezes or slows down when I'm playing the facebook games. I've tried all the software tweaks and such.
Any advice/info would be appreciated.
Thanks
Steve T.