9600GT LP vs 9600GT 1GB vs 8800GT AMP!

Hi!
I'm in a serious dilemma:I would like to buy a video card,and I cannot choose between 3 similarly priced cards: the Galaxy 9600GT Low Power version with 512 Mb RAM,a Zotac 9600GT with 1Gb RAM,and a Zotac 8800GT AMP! version with 512 Mb RAM.
My arguments are the following:
-the low power card has a bigger fan and a lower power requirement,so its probably the most quiet of the 3,and perhaps the slowest.
-the 1Gb one comes with reasonable speed and bigger RAM.But which one gets old sooner,the 512 Mb RAM or the 9600GT chipset?
-the 8800 is factory overclocked,so its definitely the speediest...but it consumes more power,and makes more noise I think.

Help me choose please!

My second question:Is a 400W PSU enough for a system with the before mentioned VGA,a Core2Quad 8200(95W TDP),1Hdd and a DVD burner?The PSU is a really good one,but even then its only 400W...

Thanks in advance for your advice!

BTW I forgot to mention that I'm not that hardcore gamer,I play every now and then and I want to keep the card I'm buying for as long as possible....

Forget about 1 gig of memory on these cards, they are not powerful enough or have a wide enough memory bus to use anything over 512meg. So throw that out the window when trying to decide.

The most powerful of these is the 8800. But today, even the 8800 is considered a low end gaming GPU. I would only buy an 8800 if they were less than $40, and you were buying 2 of them for SLI.
If you are looking for a decent card to last a while, you need to look at much newer cards, these things are 2 years old.
What is your price range, what resolution is your monitor?

you should realy consider ati 4770, quite the same (preformence wise) as the 8800GT but with lower power consumption and heats less (due to its 40 MM tech).

I didn;t like ATi too much but the newer ones have won me over!

I've got an 8800gt Amp in right now and it's going out the second my new 5870 arrives. In the apst few weeks it has doubled in volume on the fan whenever I game, so i think it's slowly giving up the ghost. But it has been a good card for it's lifetime, though it's power usage should also be taken into account if you leave our pc on all the time like I do!