Orthodux :
Well.. The wattage has nothing to do with the time of your pc being on. Also we don't know the rest of your specs, so we can't say how much power you need. I guess without a GPU and OC's a 430 watt PSU would be enough.
Heres my specs, already have the case, this is without the psu added off course, another things to note is that i alread have the apu and motherboard, got it at microcenter and the apu comes 4.0 ghz out of the box, don't know if thats a factor as well. case three 120mm fans as well.
PCPartPicker part list:
http://pcpartpicker.com/p/31M82
Price breakdown by merchant: http://pcpartpicker.com/p/31M82/by_merchant/
Benchmarks: http://pcpartpicker.com/p/31M82/benchmarks/
CPU: AMD A10-7850K 3.7GHz Quad-Core Processor ($178.99 @ NCIX US)
Motherboard: Asus A55BM-E Micro ATX FM2+ Motherboard ($53.38 @ Newegg)
Memory: G.Skill Ares Series 8GB (2 x 4GB) DDR3-2133 Memory ($94.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($79.28 @ SuperBiiz)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer ($19.98 @ OutletPC)
Operating System: Microsoft Windows 8.1 - 64-bit (OEM) (64-bit) ($99.97 @ OutletPC)
Total: $526.59
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-02-28 16:59 EST-0500)