How big a PSU and why a Corsair one?

[carbon8ed]

I currently have a TT 700w PSU with 4 x 12v rails, each at 18A. My system is a watercooled E6600 with X1950 Pro, 2GB Crucial 10th on a DS4 mobo. The OS is on a RAID10 with 4 seagate 80GB SATA drives plus 2 320GB SATA drives on the 6 Intel headers, I have 2 further 500GB SATA drives on the Gigabyte headers, 1 DVD-RW on the IDE drive and a further SATA DVD-RW on a Sil3114 PCI card.

There are 6 cathodes, a DDC Ultra pump, 9 120mm Nexus case fans and 3 thermal monitors, oh a FDD as well.

I am experiencing problems when adding additional hardrives with I believe a lack of power, it seems one of the (last one?) HDD starts to spin up and then stops causing machine wide failure to launch unless I turn everything off wait a few seconds and then start up. The CPU is O/C but running at low voltage.

I have been looking around and the suggestions are that I have too much draw on the 12v rails. I want a better PSU but there are soo many. I have looked at all the Corsair PSU stickies and found them very helpful. The 620 Corsair has 10 molex and 7 SATA connectors whuch suggests that it will handle lots of peripherals........BUT

12v RAIL on the Corsair is 50A, combined 12v rail on my 700w PSU is 54A. info suggests that Corsair use better (105C)caps (but the TT 750w does as well). i'm looking also at 700, 800 and 1000w PSUs from other manufacturers.

They are all powerful, but how will I know which PSU will successfully run my rig plus around 10 or 12 Hard drives?

I can't read across specs from the TT site to the Corsair site because the various specs are expressed a little differently. JohnnyGuru's review for the Corsair is very good and gives some good clear info though.

So would the Corsair 620w be better for my rig than my current 700w?, mine has 4 12v rails, the Corsair only 3, mine is 54A across the 12v, Corsair is only 50?, mines has 6 SATA and 8 moles, corsair has 7 SATA and 10 molex.

Must be down to internals, but my questions are:

Would the 620w be enough for my rig
Why should the 620 Corsaid out perform higher wattage but expensive PSU's
If othgers are making ever increasing powerful PSU's, why has Corsair stopped at 620w? - Tagan are at 100w I believe.

I know a lot is down to PR, but I'm hoping for some real understanding of PSU's can so different.

Thanks in advance.

[carbon8ed]

Sorry for double post - Internet went down at posting site, please delete this one.

Thanks