You can certainly do
it (well... might require some work with a dremel or body saw - don't know that case).
If the question is "will two 120mm radiators, stacked up so that the exhaust of one feeds the other perform as well as a 120x2 radiator using non-case air?", the answer is "No." Will it perform better than a single 120x1? Yes.
There's a lot of info about this over at procooling (go search for it). Look for posts by Cathar about radiator stacking.
The HPPS is very quiet - but vibrates. Get some "gel stuff" from Petra's. There's also a push-on reservoir that I've found quite useful - here's a link to a merchant's page AGB-O-Matic
but that might not fit in your case.
That pump should be plenty powerful for a single cpu block and single gpu block - so long as they're low restriction (like the apogee). You can get more performance out of that pump by connecting a couple of solder points on the control board so it runs a a higher frequency - but it will then vibrate more. It can also be set to a lower frequency, which concomitantly causes it to vibrate less...