Well first of all... the 754-AM2 watercooling kit... I know the H50 is popular... but my first loops was a single 120MM BIX rad, 355 and a tline. It was no better than high end air for cooling a clawhammer processor when OCed.
Granted it was my first loop so I am sure a good reason for that was user error. I made a few mistakes, the only one I did not fix before selling the loops was cleaning hte block and rad with a vinegar bath (did not know about that back then)
However it is a start if you are only cooling CPU
As for the pelts...
400W is excessive for a Q6600. Might be good for a 980X though. Of course.. I think 50mm might even be larger than 1366. It is about 40-45% larger than a socket 775.
Cant find info on 1366 die size.. 775 is 37.5mm and 1366 is 20-30% larger. Still not 50mm if my math is not off.
Also a single fan waterloop is not going to be enough to cool a 200+ watt pelt.
A peltier is not a REPLACEMENT for a good watercooling loop. It is an addition to an overdesigned one!
I dont want to tell you NOT to go pelt.
But don't
For the money the good loop and pelt will cost (let alone operating cost) pick up even one of the koolance v1 pots (yeah its really a dice pot... but hey.. its cheap!) and a couple hundred liters of LN2
EDIT: You posted before I finished typing :p You looking to cool your 920? whole nother ball game. To reduce a 4.5GHz 920 to ambient temps I think you will need approximately 150W-180W of pelt. Maybe more... no more than 200 i think though. A well designed 120.2 waterloop would be efficient enough for that. For subambient though... you really will want a 3 fan rad minimum.