I'd invest a bit in the CPUs as well (the more cores the better). If you're building a mining ring you might as well get the best CPUs you can as well so you can swap over to any new coin that catches your eye and not worry about if it's better to mine said coin with cpu or gpu.
You could also cpu mine primecoin VERY efficiently while mining your LTCs.
I'd rather invest in Gpus than CPUs, how profitable is prime coin
It's not profitable (unless price/demand goes up), but LTC is in that same boat right now too. Right now an alt coin mining rig would really just be a way to crank out some hashes on promising new alt coins. It likely won't be profitable as a pure LTC rig unless their value goes up.
If LTC is all you want then buying $4k worth of LTC might be the better way to go. (look at it this way: for $4k you could buy 1,333 coins, or you can spend 300 days mining 1,333 coins (don't forget cost of electricity)). It would take 10 months or so at current $ values (+ difficulty) to break even on your proposed rig (not including electricity, it adds up FAST for GPU rigs).
Yeah, I didn't mention it but I am not attached to ltc. I'm looking into fastcoin and other alts. Even some small ones which I can exchange for ltc btc. It is for fun and my goal is to make £750, I don't need to break even, and I can use the 7950s in many builds to come.
Edit : the twin frozr and vaporx cards are around £260 and the gigabyte cards are £240, so I can save £100 w/ gigabyte cards, is it worth it?