Seeking advice on memory purchase

[gibsonstu]

Hi guys, let me start with my system specs
Windows 7 Ultimate 64 bit
CPU AMD Phenom II X6 1605T Thuban 45nm Technology
RAM 8.00 GB Single-Channel DDR3 @ 803MHz (11-11-11-28)
GPU Radeon HD7870
Motherboard: http://

Now as you see i have 8gb of terrible ram ( 4 x 2gb sticks) and am looking to replace 2 of the sticks with some decent 4gb sticks to put me to 12gb. I was looking at the Gskill sniper or ripjaw, but they are slightly out of my budget of 50-60$, so i was wondering if any of you could recommend me any to go for? I think my board can only run 1333mhz ram.
Also, just replacing 2 of the sticks, will the remaining 2 poor sticks affect the performance of the new sticks?

thanks in advance for any help and recommendations.

 

[Karsten75]

Don't mix memory modules. It's a really bad idea. Get a kit of the same specifications.

At best your memory will run at the slow speed of the poor memory, at the other end, it win't boot up.

 

[gibsonstu]

ok thats good to know, in that case do you know any cheap yet decent performing 16gb kits?