Haha, wow, totally missed the part where you said you already had the computer with the Q9450 
You can get a used i7-870 for between $115-150 on ebay, or you can get a cheaper alternative, the i5-670, for between $75-110.
But, used parts come with risks of not knowing how much they were stressed.
Good thing about first gen i3/i5/i7 = they all overclock like most old CPU's before the locked everything besides K chips in the 2nd gen.
You can get a used i7-870 for between $115-150 on ebay, or you can get a cheaper alternative, the i5-670, for between $75-110.
But, used parts come with risks of not knowing how much they were stressed.
Good thing about first gen i3/i5/i7 = they all overclock like most old CPU's before the locked everything besides K chips in the 2nd gen.