With quiet builds the biggest issue at the end of the day is the pump the Hdd and PSU. The HDD are the easiest buy ssd or HDD silencing boxers (which work alright) both of which are rather expensive (but so is most good things in life). The PSU is the next issue duel passive is probably the way to go (if you need that much power the best i'v see was 550-600w and they tend not to be any good with high ambient temps however)
or maybe a thermaltake Toughpower XT Platinum 1275 W (http://www.techpowerup.com/reviews/Thermaltake/TPX-1275M/
) silent at least while idling.
Then the pumps I would recommend getting a eheim 1048 submerge it in a custom res add foam on all sides and then have a those large passive rads like so http://www.million-dollar-pc.com/systems-2008/lian-li/tremeloes/lian-li-pc-a01-htpc.htm
I have never try this set up but its the only way i think you could ever get a pump silent...... people will say ddc-1 (the quietest ddc pumps that i'm aware of ) are silent but there not. While they are not noise by any means they seem to have a noise level similar two a 1600 fan but it seems to carry really well. I have 2 ddc-1 in a custom make noise proof box (admittedly poorly built) w/ high quality 1cm thick anti noise foam on 5 of the 6 sides Its still the most noise thing in my system...
IMO you can WC anything but weather you are willing to make a custom WB is another matter..... I would still recommend having 2 fans @500rpm mark that should be silent and at least give some air flow...
I agree that 1000 fans have a noticeable level of noise it really just depends on your environmental at midday my pc seems silent but now at 2am in the morning its irritating (that said i have 21fans running at 600-800 rpm) I would strongly recommend shrouds for fans really reduces noise!
btw maybe you can find a block and make a custom mounting bracket way easier than make a whole block
GL Edited by 4514kaiser - 4/3/12 at 9:29am