oddly enough, zalmans arent really that highly looked up to in the aircooling department for their quietness (wierd, isnt it!).
Grab an Artic silencer for the 9800 if its not watercooled, and one for the 6600 (they're different models, i think, so be careful of the ones you buy). They're a really, really reasonable price too - about 25ish USD? on the 'low' speed, they're very quiet, on high a bare whisper (25db, absolute max, and its a low 'whoosh')
You could grab a yateloon or a nexus 92mm fan and mod it in place of the original one on the flower, or alternatively make a small duct + use a nexus/yate/whatever 120 on top of it. Or, you could buy an A64 freezer, as they're apparently very quiet from the get-go.
Definitely opt for the passive heatsink if possible for the Nb.
Mount the hdd's in the 5.25" bays using bungie cords + grab some heatsinks for the sides of them. Personally, id sell the drives and grab some seagates or samsungs (seagates are my personal perference). Once its quiet enough, those maxtors will start to annoy you... (If they're not already, its still a loud pc
)
I reckon the only way you're gonna get the watercooling substantially quieter is if you use an external passive radiator, use an undervolted DDC, watercool the LOT (gpu, cpu, nb, hdd's) and use a single 120mm @ 5v at the rear to clear the case air. That would definitely be quiet...