Building my first pc. need opinions and advice.

Well hi everyone, ive been lurking for a while and well i needed some help so i guess i decided what better place to ask for this stuff.
Ok ill get right down to business. I've got some parts in hand and a few that are coming/plan on ordering. ill list what im kinda stuck working with and some things I kinda need some help with.

what i have to work with-
Case: thermaltake v3 black edition
dvd drive: 24x asus dvd+rw
hard drive: western digital 250gb caviar blue
Ram: Kingston Technology HyperX 8 GB 1600mhz
GPU: ati sapphire 6870

What i need some advice on
motherboard: ASRock 870 EXTREME3 R2.0. Is this compatible with the processor below? if not recommend me a MB of similar price range.
Processor: I want an amd fx series 8120
PSU: again, im at a bit of loss on this as well. im not sure where to start but I am on a budget and well.. psu is not a good thing to skimp on. so please recommend me something

also any air cooling advice would be greatly appreciated!
thanks everyone and if this is in the wrong place please feel free to move it or direct me where to go.

Take a look my System Spec's:

MOTHERBOARD: BIOSTAR TZ68A+RCH 1155 SOCKET
CPU: INTEL i5 2500K OVERCLOCKED AT 4.7 GHZ
MEMORY: 16GB PC3 12800 1600GHZ G-SKILL RIPJAWS X SERIES
VIDEO CARD: ASUS EN9500GT 128 BIT 1GB MEMORY
PC CASE: COOLER MASTER HAF 932 BLACK EDITION
PSU: OCZ MODXSTREAM 700 WATTS MODULAR 80+ CERTIFIED
OPTICAL DRIVE: LITE-ON 24X DVD WRITER/READER OEM
HEATSINK/CPU COOLER: COOLER MASTER HYPER 212 PLUS
HDD: 160 GB AND 200 GB HITACHI DECKSTAR 7200 RPM
NZXT SENTRY 2 TOUCH SCREEN FAN CONTROLLER
KEYBOARD/MOUSE: GEAR HEAD WIRELESS KEYBOARD AND MOUSE
OS: WINDOWS 7 HOME PREMIUM OEM

P.S. I overclocked my CPU at 4.8 GHZ and very stable considering that my motherboard is not a high end MB like ASUS, Asrock, Gigabyte etc...?