My biggest concern with putting the rad at the bottom would be the cards in the mobo, and their height interfearing with the rad, and the other thought for that is, where you'd mount the pump, the PA 120.2 is a lot fatter than the pictures make it look, I was surprised when I got it out of the box.
A 120 and a 120.2 would add more flow restriction, yes, I was just offering possible alternatives if you were set on 120.3, which you're not so no worries there
If you go external for the pump/fans then there's a certain amount of noise dampening you can do to kill most of the sound
Anyhow. As for the side fan, I'm not sure, it depends on your positioning of things really. Ideally, I'd be happier if the air was going through the rad and straight out of the case, rather than pushing warm air into the case. I'd say your best method deciding where to situate your rad would be based on tubing curves/right angles and block placement/reservoir placement. I'd have liked mine to be lower than it is, for example. It will be soon, but hey. I'd advise against moutning it horizontally above the case, for air bleeding reasons, I have enough trouble with mine being near the top
If you could construct a sufficient support, vertically from the bottom may be an option (Mechano is good for that, my Xbox and Gamecube swear by it ). If that comes into contact with the side fan area, you might be able to attach a fan on the opposite side to bloe in the same way as the side fan. I'd not want to go external on the right hand side of teh case (Looking from the front) because it's already pretty heavily biased to that side as it is.
If you planned it right, though, vertically a dual 120 in the front bays may be the ticket. It'd be quite possible to lose six bays and have the HDD's in the rear HDD area instead of the shipped cage, that'd also leave two spaces for future work, if you fancied modding the shipped cage to accept an 80 fan and two in two as oppose to three in three.
If you can, try drawing it, doesn't need to be to scale, unless you like it that way, it might give you more of a feel for the location of things, it helps me trial and erroring it with paper rather than a case itself Costs elss, too. One thing about mouning the drives at the back, because it's at the top, check that your chosen drive interface cables can reach, be it SATA or IDE.
Oh, one thing about the PA120.2 (Not sure if it's true of the other two sizes) the shipped screws will be FAR too long and will puncture the radiator without the gasket, which tends to rip (I've had two rip on me. Out of two.) I ended up using shome shorter, blunt, metal self-tappers I think mine were two mm shorter than the shipped screws, not exactly sure any more, I can check if required.