Q9300 run on a low 7.5x multiplier, so it would be fsb limited, not heat. That liquid cooling won't help you.
Q9300, when ran at 1600mhz (4x400) fsb, would be 7.5x400 = 3.0ghz. For comparasion, a q6600 would get 9x400 = 3.6ghz at the same 1600mhz fsb. You have to look up your motherboard fsb to get an idea on how fast you can oc.
Also, note that q9300 use 6mb(2x3) cache, compared to q6600's 8mb and q9450's 12mb. It will perform lower per ghz.
