Well I am running all the fans (Bitfenix Specre Pros - 200mm x3, 140mm x3 120mm x1) off the stock 3 speed fan controller that come with the 630 so I've no idea as to the RPM as nothings plugged into the motherboard lol. They are not too bad on setting 2, if I go down to 1 then I can just hear my DCP 4.00 water-pump over them so theres not much point.
I've not tried dual 120/140 fans instead of the 200 but bigger usually means quieter when fans are concerned. (Oh BTW the Bitfenix 200mm are not a direct fit, mounted the front one on 5mm standoffs and cut the 2x200 roof ones down with a hacksaw, have pics if you are interested.)
I was originally gonna go with NZXT fans but they were a pain to find in Green LED at the time so went for Bitfenix instead, got them hooked up to an LED controller so I can turn the LEDS on and off too.
I actually suggested the NZXT full window side panel in the products suggestions forum but unless NZXT put them on the OCUK price list they can't get them so I've ordered one direct from NZXT in the USA for about $80 USD