The zalman case looks the quitest but the LIan Li cases are nice.
you can get a "pre quited case" like that zalman, cosmos 1000, nzxt whisper ect..
Or you can get a somewhat quite case, like those Lian LI and countless others, and sound proof them, which sound absorbing foam, rubber fan mounts, silent fans, rubber psu mount, rubber feat, rubber side trim, hDD silencers, and so one.
It might seem like a lot of stuff, but it is relatively cheap and you will probably get a quieter case.
If you want supper quiet then do both, get a nice quiet case find out what makes the noise and fix it.
anything secc and .8 or better is about all you can ask for.
A modern one with bigger than 80mm fan for the case is even better...
if to stick to original atx standard and reverse cool with psu up top...the best,
and maybe a front cover.
I go for cheap. My last exotic was a 2600amb builders case, (its a fat one)
other than that, do whatever you want. the aluminums make me nervous, unless a little aluminum , (like the casetronic c4117) for a big case, you want the secc "radio metal" for your big board. The little cases canlt give away enough and have an excuse.
I build a system with requirements very similar to yours - I have a Radeon 5870 card, the case is silent and all ports and buttos are at teh top of the case. I chose a Raven RV02 from Silverstone and will never look back. If you do some research, you'll find out the the Raven cases have a roteted motherboard mounting system - all your components face upwards. There are 3 180mm fans at the bottom of the case and they are blowing right onto each component - no longer is the CPU fan obstucted by the gfx card. I really don't understand why noone thought of this principle before Silverstone. I simply cools better than ANY convetional case, period. Just be sure to use a towe cooler, so it maximally benefits form the case rotation.
My CPU is overclocked, yet all the fans are set to 700 rpm and I never reach 50 C. And it is "almost" silent - the Radeon 5870 makes some noise while under load, but when idling, it's not hearable.