How Much Power Do I Need?


I am currently looking for parts as i am building my friend a gaming computer. The computer is a mini-itx form factor and i have found all the parts that he likes and everything that is compatble. My question is how big a power supply do i need to power all of the things that i am putting in this computer. I was looking at a review for the gpu and it said that the gpu needs at least 400W so im not really sure how much power i need now. Here is a list of parts:

Motherboard: ASRock DDR3 1333 Intel - LGA 1155 Motherboards (B75M-ITX)

CPU: Intel Core i5-3570K Quad-Core Processor 3.4 GHz 4 Core LGA 1155 - BX80637I53570K

Ram: G.SKILL Ripjaws Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-4GBRL (This Ram was compatible with the old motherboard but then i got a different one so ill have to check that)

SSD: OCZ Technology 128GB Agility 4 Series SATA 6Gb/s 2.5-Inch Solid State Drive(SSD)

GPU: EVGA GeForce GTX 650 2048MB GDDR5 DVI mHDMI Graphics Card 02G-P4-2651-KR

Case: BitFenix Prodigy Midnight Black

Those are all of the parts and hopefully you can help me with the power amount that i need. Feel free to add any sugestions as to things that you think i should change aswell just make sure that you post a power amount for the changes aswell otherwise i will be stuck in the same place again.



and dont forget to get i bit more than you need.

I always play it safe when I do a build, so I'd recommend a quality 550w.  80+, single 12v rail, and a reputable manufacturer (corsair, seasonic, antec, etc)

Agreed /\/\/\/\

thanks guys