Noob in need HTPC build

Hello community, first off i have a pretty good understanding of how things work and all but when it comes down to specific parts its hard for me to distinguish what would be best. I am building an htpc build/gaming build. i would like to play games on somewhat high settings but also i want to keep my budget pretty low its mainly going to be used for blu rays and winamp (milkdrop for parties!) I am just going to list what i purchased, what i have on hand, and what i plan to buy. let me know what you guys think and recommend it would be very much appreciated.

bought case - Raygo Micro atx

bought mobo - Biostar a880g+

have CPU - AMD Athlon II x3 3.3GHz

planned ram - AMD 4gb 240-pin DDR3

have GPU - PNY GeForce GTX 550

planned Drive - Asus 12x BD-Rom

need power supply - what is economical and functional

have HDD - seagate 160gb sata

I went with the that specific mobo because ive heard that a lot of people have had success unlocking 4th core on amd athlon II x3, i am concerned that by cpu will bottleneck by build if i cant fully OC. But yea so thats probably way longer then it needs to be but what do you guys think? Keep in mind that i would really like to use what i already have because its not that terribly old... is it? :s