Hi, guys. I have about £2500 to invest in litecoin rigs. One of the rigs is a replacement for my Sandy bridge rig and will be a gamer/miner, I will use it to game maybe 4 hours per month. The other rig is a cheap AMD platform. The haswell rig will run with my 7970, a 7950, and a 6950 I will purchase. The AMD build will run 4 7950s and a 6670 or super-budget card for displaying the screen w/o compromising the stability of the cards that are mining. Is it possible in cg miner or guiminer to only mine with four of the five Gpus I will have connected?
 
Here are the two builds, can they be improved?

Gamer/miner
I5-2500K
Gigabyte GA-Z68X-UD5
XFX 7970 (owned)
Sapphire vapor-x 7950
HIS or Sapphire 6950
Corsair HX1050 (owned)
Lian li T60
Optical drive, win7 h

Edit : updated build

The 7970 gives around 600kh/s, the 7950 should give around 600 too and the 6950 will get 400-450
Total hash rate : ~1600kh/s

AMD
Athlon ii x2 270
Gigabyte 990FXA-UD3
4gb ram
4x sapphire vapor-x 7950
6670 (to power display)
OCZ 1250W psu (might get a 1475w to be safe)
Optical drive, win7 hp
7950s will give around 600 each so 2500kh/s should be achievable. 6670 will give around 50kh/s should I decide to mine with it too.
Total hash rate : ~2500kh/s

Combined hash rate: ~ 4100kh/s

Thanks for your time!