^^ +1 to that and if Op can OC it somehow [ though most OEM mobos don't support this ] by bios or Setfsb around ~3 Ghz maintaining the thermal limitation then it will greatly enhance the performance.
Only cpu upgrade I can thionk Op can go is for a Q6xxx or Q8xxx series LGA 775 cpu but they are EOLed so second hand deal is the only option here and with such cpu a psu upgrade is a must.