New PC, 2 x WoW

[Bitzy]

Hey all

My five year old pc is dying and I need to buy a new one. Hoping for some help here to decide what I need to get. =)

I run two WoW at the same time, only by alt+tabbing, no extra software for multiboxing and no extra screen.
At the same time I would like to be able to watch movies, listen to music, browsing the Internet and maybe play around a bit with graphic software, like photoimpact or photoshop... (+ things like MSN, Ventrilo, Antivirus, mouse/keyboard software and such)
I don't need the system to run on max settings when playing both accounts but I would like to be able to play on rather high settings when playing only one account in raids, bg and such... I am using screen resolution 1680x1050.

I have been looking around for some good setups but I feel so lost and I haven't really been able to get any help =/

I was thinking about i7 but that seems just way to expensive for me so I think that maybe i5 or AMD would be better...

Two systems I have tried to setup:

Antec Three Hundred
Asus M4A89GTD PRO/USB3
AMD Phenom2 X6 1090T 3,2GHz BE
2 x Corsair 4GB (1x4GB) 1333MHz XMS
Corsair VX 550W 80+
Sparkle GeForce GTX 460 1GB OC
500GB Samsung Spinpoint F3 HD502HJ
Windows 7 Home Premium 64-bit OEM
Cooler Master Hyper 212 Plus

Antec Three Hundred
Asus P7P55D-E PRO
Intel Core i5 760, 2.8GHz
Corsair 8GB (4x2048MB) 1600MHz XMS3
Corsair VX 550W 80+
Gigabyte GeForce GTX 460 1GB OC
500GB Samsung Spinpoint F3 HD502HJ
Windows 7 Home Premium 64-bit OEM
Noctua NH-U9B SE2

Some questions about the systems:

1. I have never overclocked anything, is it possible to do that as a total newbie without messing things up? Mainly thinking about the i5...
2. Memory. As you can see in the first setup there are 4 sticks - and in the second there are 2. Does it matter in the way of performance or anything else if I pick 2x4gig or 4x2gig? The price for the two different ones are about the same but I can ofc see that the MHz is different, is that a big deal when it comes to performance? Is it even possible that I can go for a total of 4gig memory without problem?
3. I have been reading that the cpu fan is a problem for both the AMD and i5 - as in loud and not that good to keep the cpu cool - so I guess I should get a replacement for that. I really don't know what to get but I have seen good reviews about both the fans above, so can I just go for the cheaper one..? :s

Don't know anything about motherboards, I just want one that will last for some years, I will not be using SLI so that doesn't matter, the above graphic card seems to be good for the price.
I will not build it myself, the shop will before they send it. Also, the above mentioned is all that my budget will handle - if I could I would like to get it down even more but I really don't see how...

I would be so happy if I could get some opinions about this because whenever I mention that I will be running 2 WoW on the system no one seems to be able to tell me what I need... I would like to get it asap since my pc is very unstable and Cata is just a week away =) Hopefully my spelling isn't too messed up, Swedish player here and I don't think I get everything right ^^

Thanks