Assuming you are not CPU, bandwidth, or driver limited, 4 cores should outperform 3.
bandwith will ofcourse be limited since you have
(2 * 16) / 4 = 8 lanes per core versus
(3 * 16) / 3 = 16 lanes per core
Q9450 @3.60 Ghz, Striker II Formula, Evga 9800GTX (863/2050/1200), 2X2gb 1100 5,5,5,18 D9's at 2.20V
Cooled by: MCR320, D-Tek Fuzion V2, MCP335 w/ EK G3/8 TOPS, Full BP high flow 1/2" fittings
Oh and Vista Ultimate (i know, I KNOW!)
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