i would highly recommend
the eheim 1048 pump, it performs much better than the 1046 and can be quietened down to near-silence with careful dampening. a 1046 would be too weak in my opinion unless you give it that innovatek mod which bumps it up to 1048 performance...
a BIX is not really going to give you performance and silence together, i learnt that the hard way. i would HIGHLY recommend you go out and find yourself a heatercore as you will be able to run 2 fans on it at extremely low speeds, i'm running 2 papst4412fgl's on my heatercore and my monitor is still the loudest component in my system.
you should be able to find suitable brass barbs for the 1046 (if you end up getting this pump) that converts the outlet to 1/2". (iirc the inlet is already 1/2"). look to your local plumbing supply warehouse, down here in australia a good one is Purple Pig
, to give you an idea of what to look for.
when you're watercooling, the noise that you have to deal with comes only from the pump and the fans on the radiator. eheim pumps are top-notch when it comes to noise/performance, and wrt a radiator, just find a nice big 2x120mm2 heatercore.
that's your ticket to silence.