Seriously.. no need to replace 4850, when other parts of your system are far behind in performance..
1. E5200
2. 2X2 GB Transcend 800MHz RAM
3. 22" LCD but don't know which one??? Budget Max 10K
^^^
Wise decision, also still you wud need to overclock your proccy.. a litle, your Ram went kaput 'cause you did something wrong obviously.. see some overclocking guide or better ask for settings(moderate overclocking) here based on your mobo.. regarding monitor, both are praised heavily.. samsung service is ok if you are in a city, no idea about benq..