Fortunately for you, your motherboard does support the LE1640, but you will have to update the bios to version 1.8, do this BEFORE you remove the 3000+.
Once you've updated the bios all you have to do is swap the CPU's and everything should work just fine.
------------------------------CPU: Intel Core i7 920 @3.2Ghz, MOBO: Asus P6T SE, RAM: 3x 2gb OCZ Platinum OCZ3P1600LV6GK, GPU: Sapphire HD 5870, PSU: Corsair HX520W, HDD: Seagate ST31000528AS 1Tb 32mb, COOLER: Scythe Mugen (S775 version), CASE: Coolermaster CM690
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