Upgrade time, advice required.

Short story :

PC Spec was :

AMD 955BE
Asus M4A87TD EVO

I sold these as i planned on upgrading straight away, however due to having to get a new clutch and DMF in the car the upgrade was postponed. Ive decided to try the Scan 9 month finance option as it would just tie in with the way things are atm for me.

Ive been using my media pc mobo/cpu which is :

AMD 550BE unlocked to tripple core and oc'd a little
Asus M4A785TD-M EVO

However, i want to get my media pc back together so im looking to upgrade, the current components i have are :

Corsair 800D case (This will stay)
Corsair HX520W PSU (This has served me well over the years, do i need to upgrade this psu?)
XFX 4890
Corsair H50 cooler in push/pull with noctua fans
Another 3x 120mm noctua case fans, and 2x 140mm case fans.
80GB intel SSD
Samsung F3 1TB
Corsair dominator 1600mhz 2x 2gb.
24" Dell @ 1920x1080 (This will stay)

I dont want to spend too much but i want something that will last me, only really a casual gamer but ide be lost without my machine, its where i spend ALOT of my time (IT Tech).

Im thinking sandybridge..but do i go :

i5 2500k or i7 2600k ?
Which motherboard ? According to custompc the p8p67 is the board of choice..however i feel its a bit "poverty" so to speak, my mate runs the p8p67 pro and loves it. Is that asus sabertooth any good?
Do i need to upgrade the ram ? Purhapse 2x 4gb sticks ?
Do i need another PSU, i feel the 520w is low compared to whats being used nowadays.
Which GPU do i go for, i initially thought of the GTX 570, however the MSI GTX 560 TI seems to be proving very popular.
Do i need a diff cpu cooler to tame the i5/i7, i do plan on overclocking i probably should of mentioned this earlier on. I could always migrate my h50 to my media server if needed.

I think thats everything ide like advice on tbh, and i am an AMD fan boy, no denying it, however i want a system NOW i dont want to wait for bulldozer, i fancy a change and these sandybridge chips seem to be very tasty.

Thanks in advance fellas !

The AM3+ motherboards are being released ATM so TBH if you had kept your Phenom II you could have plonked that in one and got a Bulldozer CPU when the Phenom II ran out of steam. AFAIK Bulldozer is out at the end of June.

If you are gaming the Core i7 2600K is not really worth the additional cost over a Core i5 2500K IMHO.

I would get an HD6950 2GB especially the revision one version which has a good chance of being unlocked to the same number of shaders as an HD6970 2GB. You can also get th HD6950 1GB for around £170 to £180 too.

With regards to the RAM I would make sure that it can run at 1.5V to 1.58V as anything above this is above the "safe" limit for Sandy Bridge(I suppose you get away with running it higher but it could lead to issues in the long run).

You need to get a P67 motherboard if you want to overclock although in the next few weeks the Z68 is being released. Gigabyte is stopping production of the P67 motherboards and is replacing them with the Z68 chipset AFAIK. The Z68 has additional features when compared to a P67 motherboard.

If you don't intend to overclock I would get an H67 motherboard instead. The K series processors also lack some virtualisation options the other Core i5 and Core i7 processors have although they use the faster HD3000 IGP.

I would have waited a bit longer for the bulldozer. You can just use your htpc for the moment in time.