My XP1800+ puts out over 50w of heat, and running at 100% CPU for 18 hours a day it didn’t actually need a case fan, just a CPU fan and the power supply one. I only added case fans when I played with overclocking and, well, because they have lights on them.
Is it this the flower cooler you were thinking of
http://www.quietpc.com/uk/amdcooling.php#6000 or the other one? If it was that one were you going to use the fan provided or not?
Anyway I think you should be OK with any of the flower coolers or similar and that PSU. I would certainly attempt it with that anyway, keeping an eye on temps and having a motherboard monitor log and auto shutdown running also.
That PSU has quite a good noise rating and supplies 28A on the 3.3v rail which is not bad at all for 350W (mine, a QTec unit also rated at 350w, only does 14A which has lead to many problems).
I don’t really know anything about that motherboard I’m afraid.
I have a Samsung SP1614N hard drive and I’m amazed at how quiet it is, I thought my older Seagate one was quiet until I used this. Mines 160GB (not sure if they do a 200GB in the same series so don’t know if it would be the same noise level) and for 7200 spin speed with 8meg of cache it performs well. Are you thinking of getting a hard drive silencer enclosure?
I’ve used a Sapphire Radeon 9800 graphics card, again passively cooled, and was quite impressed with it.
Let us know how you get on with this project, as you can tell I’m interested in the idea