To find out what other people have gotten in terms of hash rate for a specific card, look at:
https://litecoin.info/Mining_hardware_comparisonA lot of times the brand will dictate how well the cooler works. You'll need cards with good coolers for mining. In general, XFX cards have terrible GPU coolers and should be avoided. Small differences between models of the same brand shouldn't matter much.
The power supply you need depends on which card you're going to run and how many of them. The 7950s can eat up 300w each if you overclock and don't/can't undervolt them. You'll probably need riser cables to space the cards apart for cooling:
http://www.ebay.com/itm/111254627706You don't need to worry about grounding/earthing anything. I run rigs in plastic crates all the time.
thanks for your reply i guess ill need to decide on a make of card and stick with the same ones i think, the 280x's seem most appealing at the moment. so im looking at 1200-1500w then. i may go for a 1200w then if i want to overclock i was thinking of perhaps running a decent 300-400w psu jump start it to supply 1 card then use the other psu for the other 3. thats if thats an acceptable solution?
glad i dont need to worry about grounding or anything that makes things somewhat easier. could i mount motherboards to wood bases? of course ill either need to have the screws loose or use washers/spacers underneath to allow room for the soldering joints and any plates under there if any.
so what im getting from this now is:
motherboard got one
cpu got one
ram got some
graphics cards 4 x 280x's
psu 1200-1500w
small hard drive.
thats another thing i havent thought about is hard drive is there a cheap easy way to put a basic os on something? i assume i probably wont be able to run an os off a memory stick/card?