I am in the middle of building a new system (looking to build a monster/killer system). I've pretty much decided what components I want to get, the only problem is I have no clue which Power Supply is needed/recommend. I am not looking to be cheap (money isn't a huge issue) but still wish to stay resonable.

My new system profile is the following:
[Profile]
CPU: INTEL Core 2 Quad Q9450
MOTHERBOARD: Asus X48 DDR3 (still debating on which one)
VIDEO: ASUS/SAPHIRE 4870 (Arctic AccelS1 rev2 with dual fans)
RAM: 2x2G OCZ DDR3 PC-12800 1600 MHZ (Platinum or Reaper HPC)
HDD: 4x Western Digital SATA2 500GB
2x Western Digital PATA 320GB
Case: Full ATX Tower with 5x 120mm & 1x 200mm fans

Question is...
a) how powerfull of a Power Supply do I need? 650W? 700W? etc...
b) what are the prefered manufactuers & models?

Any advice would be greatly appreciated.
Thanks,

A 650w is more than enough if it is a highend psu. Corsairs psu´s is a good choice.

I wonder if the 750 TX is still strangely cheap at newegg.....

well corsiaris definatly a prefered manufacture, as well akasa, seasonic, coolermaster, hyper... as long as it not X branded or 'roswill' lol.

for a build like that i would go exclusively with a modular PSU. although i do like the western digital HDD's, i cant help but think that 3 640gb would be better (or even 2, or 4 if you afford it) becasue the 640 only have 2 platter (2 * 320gb) which is an extremely high density.

also if you got corsair RAM, i think on domintator series you get those '88' fans, just pointing out great for overclocking.

Definitely go with a modular. I would also look at the efficiency rating - try for an 80+ rating. The higher the better.