Haha yes it's a nice feeling when collecting coins considering the price of LTC just went up but so did the difficulty 
If you're planning on running 3 GPU's or more on risers, then you'll probably want to make one of the GPU's use a powered riser. You'll avoid burning out the mobo and possibly the cards in the process from all the power draw. 2 is fine tho, mine are on powered risers but I have not utilized the molex connector on them at this point in time and they seem to be doing great without them. When I do add another GPU I'll definitely be plugging one of the molex's in, the last thing I'd want is to ruin 900+ bucks worth of hardware over a silly power overload 
700kh/s is a great rate to start off with, you'll be even happier once you get all your gear out into the open and are able to sail past 730kh/s with ease. If you're really keen, repaste the GPU Heatsink and you would probably squeeze a bit more out of the card.
If you're planning on running 3 GPU's or more on risers, then you'll probably want to make one of the GPU's use a powered riser. You'll avoid burning out the mobo and possibly the cards in the process from all the power draw. 2 is fine tho, mine are on powered risers but I have not utilized the molex connector on them at this point in time and they seem to be doing great without them. When I do add another GPU I'll definitely be plugging one of the molex's in, the last thing I'd want is to ruin 900+ bucks worth of hardware over a silly power overload 700kh/s is a great rate to start off with, you'll be even happier once you get all your gear out into the open and are able to sail past 730kh/s with ease. If you're really keen, repaste the GPU Heatsink and you would probably squeeze a bit more out of the card.