I also think that the 400 w Silverstone PSU is marginal. Specs say that the operating temperature is 0 to 50 deg. C. From the mtbf figures, rated output is at 25 deg. C. (room temperature). Based on data that I have seen from various PSU manufacturers (at least those who do publish data), you need to derate the output by about 1% per deg. C. over the rated operating temperature. That basically means that at 40 deg. C (a more likely operating temp.), your 400 watt PSU turns into a 340 - 350 watt PSU.
A lot of the "better" PSU's specify full rated output at 50 deg. C.
Here's your cheapest deal and still get a quality PSU. You can get the 380w version, but is only about $3 cheaper. This one has a little more upgrade path than the 380w EW one, so I'd recommend this one on a tight budget. $60 shipped - $30 MIR = $30!!!
Antec earthwatts EA430 ATX12V v2.0 430W Power Supply 100 - 240 V UL, CUL, FCC, TUV, CE, CB, C-tick, CCC - Retail http://www.newegg.com/Product/Product.aspx?Item=N82E168...