A PSU thread and nobody has linked a PSU calculator?
Tisk tisk. FYI, that calculator gives "recommended" wattage which by my estimates is based on ~60% load on the PSU at 90% system load. I use 25% capacitor aging BTW. Include any planned or potential additions and you don't need to exceed what the calculator spits out. CPUs and GPUs draw the most power for a single component and they're progressively using less power to deliver more performance.
Also, in general, PSUs with 80PLUS Gold or Platinum ratings use higher quality components (common sense, I know) that should last longer, but will also cost a bit more. The Rosewill Capstone 450W
PSU is a Gold rated PSU that's relatively inexpensive. (review here
I'm not saying that an 80PLUS Bronze unit from Seasonic, Corsair, or Antec is junk and would fail, those would be my recommendations if you're looking for lower cost. Heck I've put Corsair CX 430s
in a few rigs. The fact that they regularly sell on newegg for $20 after MIR is unbeatable for a budget rig.
What are your complete system specs?
Main: i5-3570K, ASRock Z77 Pro4-M, Asus GTX660 TOP, 500GB Crucial BX100, 2 TB Samsung EcoGreen F4, 16GB 1600MHz G.Skill @1.25V, EVGA 550-G2, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Crosley D-25 Case Mod