New mobo, please adivse

Ok i'm just looking for a bit of guidance from people with better experience than me.

I'm building my first rig, but am now without sufficient money to complete it (i'm a 17 year old student, spare me!) until next payday. I have so far: Case, 550Wpsu, 2Gb corsair XMS2 DDR2 ram, E8400 on order + arctic cooling freezer 7 pro.

Basically, I can't decide what mobo + gfx combo to go for. Should I buy a PCI-E 2.0 mobo or save the £30 and get a better graphics card? My two setups were:

Asus P5N-D with a 8800GT (PCI-E 2) - the expensive option

Asus P5K with 8800GTS - the not so expensive option

Another point I was unsure about was the overclocking ability of the chipset on a P5N vs P5K? I've heard very good things about the IP35 chipset and wouldn't want to waste the awesome potential of a E8400. I'm not really looking for an SLi system, so would I be wasting my money on the P5N? I just couldn't find any other reasonably priced PCI-E 2 mobo's...

Let me know what you think!