upgradeing alot of stuff and have questions

I'm going through upgrades to my PC. I'm trying to work out what I should get to improve all areas of my PC to play newer games. currently this is what I have

Dell Dimension E521

AMD Athlon 64 X2 +5200 2.6 ghz dual core (windsor)

Dell 0CT103 motherboard

2 gig ram

Nvidia geforce 7300LE 512 mb

Windows XP media center

Here is what I am adding

2 gig ram

HIS Radeon HD 4670 IceQ Turbo 512

my question is can i upgrade my CPU? What is the max chip that my MB will take. If i can upgrade how will that work with my other upgrades and the power supply. (I don't know my current power supply, but if there is a way to tell without opening the PC that would be great)

I would pick a different PSU then the one suggested. Other than the Toughpower series, I do not trust any PSU from Thermaltake.

Here is a better unit IMHO, Antec Earthwatts 500w, for only $5 more, and if the TT does not have free shipping then the Antec will be the cheaper one overall.

Thermaltake make good psu's 04dcarraher