You could try setting up a couple oil coolers, which is more or less what the Reserator is based off of. You'll probably want an Eheim pump too, if you're going for silence, probably a 1250 or 1060 with the amount of tubing you're going to have, and I assume you'll watercool the GPU too. The only thing is though, I think the oil coolers might be aluminum if I remember correctly. Maybe try a crapload of soft copper tubing instead, like the Xice passive cooler?
The Xice:
Of course, they use 8mm tubing and there's about 10 meters of it but maybe to improve flow you should use 1/2" stuff and put a low rpm 120mm fan at the top. Get a SilenX and you'll never hear it. The few people who've had passive watercooling kits have said they greatly benefit even from a very low rpm fan blowing on it.
Your temps won't be great, probably only about as good as stock heatsink temps, but it'll be damn near silent.