if you're using AS5, then yah... but don't use AS5, lol. Use one that doesn't need time to cure and isn't electrically conductive... like MX-4, PK-1, NT-H1, or DC1. Personally, I use MX-2, since I bought a bunch of it in bulk for really cheap when it first came out, lol.
What cooler are you using?
Antec KUHLER H2O 920 Liquid Cooling System - Newegg.com
This Juan! Well its the 620 that I modified to work the same as the 920 with fans on both sides