How much power is too much power

Toms did a review of he GTX295 in SLI on an I7 clocked at 4.0 using an 850 watt Coolermaster, I don't think you have to worry about running a pair of 9800's on a Corsair 850.

I am running an i7 920 @3.8Ghz, a RAID array and 2 GTX 285s in SLI on the Corsair 850w power supply with no issues whatsoever.

mmm - thanks for all the replies. Im glad i dont have to spend more than i thought i might have to!

There are a few reasons for that
1. They sell PSU's and they want as much money from you as possible
2. They are covering their ass because as PSU's age they start to lose efficiency and their max power output decreases
3. Not all PSU's are created equal

850 is plenty and I agree with the poster above that a 750w from a quality company such as Corsair or PC Power would be powerful enough.

Nothing.

^^maybe he allready has them from the old rig...

anyhow 750 is plenty since sli'ed 9800gtx use like 220W on their own, 150W for little OC on the i7, 10W for each drive and 20 for mobo and you'll end up around 400W total... heck even a nice quality 500W unit would work, and here are some nice links:
http://www.xbitlabs.com/articles/c [...] ttage.html
http://archive.atomicmpc.com.au/fo [...] t=9354&p=0

I didn't mention it earlier but as a couple before me mentioned there are better solutions that 9800GTX SLI, the only way I would do that is if I had them already. Most X58 boards support both SLI and crossfire and here you could get the 4870 for about the same price as the 9800GTX.

SLI is great when it works. Not all games scale well which is why most suggest you should get the single best card you can afford. The 9800GTX is overpriced which could actually work in your favor if you were to sell the one you have on craigslist or ebay and use the money you get toward a faster single card. Say you were to get $70 or $80 for it you could buy a couple 4850's and crossfire them and end up spending less money for the same performance. The cheapest 9800GTX+ on Newegg is $115 after rebate. Assuming you could get $70 for the card you have now it would give you $185 toward a new card. You could get a 4890 for around $160 or add about $20 to it and you could get a GTX275. The point is that there are a lot of options and you should look at several of them and figure out which is the best for you and will give you the best return on your money. Since the 4890 and GTX 275 are pretty much on par I personally find little reason to spend the extra $50-$60 on the 275.