PSU Recommendation for 4850 Quad build

Hi, as it says im just looking for recommendations.
Any help is appreciated.

Build is:

Phenom 2.2 Agena 9500 (got it cheap!!)
Biostar Tforce 790Gx Mobo
500Gb 32mb Cache 7200Rpm Hard Drive
ATI Asus HD4850
OCZ 2x2Gb DDR2 800mhz
20x Sata DVD RW drive
Zalman CNPS 9700 CPU Cooler (not 100% but will be similar)
Antec 300 with possibly an extra 2 120mm fans (as the Asus 4850 and the 9500 proc are reported to run HOT!)

http://www.ebuyer.com/product/124922
Arctic Power 500w PSU is what im looking at so approx a $50 dollar budget

Ive estimated my power output to be covered bu this by a good 100w, and i liked the dual fan spiel for extra cooling.
However, im a PSU noob so i need to know if im being drawn in by some marketing crap.


Thanks

Additional things that factor into this are do you intend on OCing the Phenom and 4850, OCing does change power draw, but you should still be good with only the one 4850.

if you're gonna crossfire them, then you need to spend a bit more on a good power supply. i'd get one that's 750watt or so.

Ive decided against 2 cards, if it comes to it i will purchase a different PSU and spend a good lot of cash on it, for now im going to stick with the above (actually got the 600w model for a quid less on a special deal!) just to get the system running.

I really appreciate the help though, many thanks! (Good spot with the 6pin 2x3, 0mg_1ts_m3)