dx2300 spec says "Intel 946GZ chipset". The only CPU mentioned is Pentium D, max 2GB RAM.
Chipset spec says "up to C2D E6700, CQD Q6700"
Unless you have that CPU in hand, I'd not invest a single dollar on this PC. If you choose to do it - make sure you update BIOS first, and read thru BIOS' Release Notes for any clues on CPU support.