Let me see...
(Regarding rad placement in OP)
Guess work:
CPU: 200 watts (89 watts standard peak?, 3.0 ghz @ 1.8 V = 192 watts?
See OC clac)
VGA: 100 watts (92 watts standard peak, allow for slight overclock)
Pump: 10 watts (unless overvolt?)
Flow: ~3 LMP (conservative)
More Guess work:
4,187 J*L*C/s for H2O
3 L/60 s = 0.05 L/s
0.05 L/s * 4,187 J*L*C/s = 209.35 J*C/s (J/s=watts) so
209.35 watts*C
Anecdotal summary:
So if your Storm is passing ~200 watts a second from your Opy to the water then you should see ~1 C difference when comparing the "in" water temperature with the "out" water temperature. (This is a pretty BIG assumption, in reality there is probably much less change in temperature than that, too many variable ignored to list.)
Anecdotal conclusion:
With the above in mind...
It is doubtful you would notice any difference by putting the rad immediately after the CPU vs. in any other part of your loop.
-------------------------------------
(Regarding last post made by "Cyprio")
Just guessing...
If you have your PA160 + 120.2 in the loop, then you would be able to run your rad fans at a lower voltage for the same or better cooling. About how much better and at what voltage....
....is beyond my ability to form conjecture.
Good luck!
Edit: I am execting and hoping someone with more knowledge on the subject will come along and crucify my post. Thus re-filling my leaky head.