5 GT 430s isnt a good use of money on video cards, what do you plan on using the system to do? I assume it involves about 10 monitors, if thats the case then you might want to pick up 5 5450s instead, they will use less power(20W vs 50W for the 430) so you could get by with all of them on a good 450W unit instead of a 600W unit
@OP, tell us what you plan to use this system for, your choice of graphics card is very poor for every use i can think of. It has a low price/performance ratio. as said above, if our just driving lots of monitors, most amd/ati cards can drive 3 monitors per card and there are some that can drive more again.