Antec MINUET 300 PSU fan noise

[tempoct]

Hi,
I've just build a machine for my g/f. Got this case because it looks sleek.
http://www.antec.com/us/productDetails.php?ProdID=15102
I have 3 fans in the case, CPU, PSU and case fan (antec tricool 80mm). The case fan is quiet at low speed, which is OK. CPU fan is currently stock HSF. Not silent but not too loud. My biggest problem is the PSU fan. Man! unexpected.
Any tip on quiet down that fan? It's hardest to reach for sure. The PSU is 300W and has a 80mm fan. I guess the fan is directly connect to the 12 v rail...
Thinking about replacing the PSU fan but that would void warranty, isn't it...