I would go with the 9600GT.  It will perform more than twice as good as the 9500GT and will work fine on a 350 PSU.  THIS ONE seems to be the least expensive one out there plus it is factory overclocked on the core by a bit and a good brand.   There's really no reason to spend more than this for a 9600GT and no reason to get a 1GB version unless you just happen to have a very high resolution monitor.  You would probably find very little difference in performance if any at all between the 1GB and 512 MB in a 9600GT.  Higher-end cards capable of playing games at those higher resolutions and settings would benefit from more video ram, but I don't think the 9600GT would.  I have played Crysis which is a very demanding game on a 512 MB 9600GT. 

Note that these cards may not perform up to their potential on the newer and more demanding games given that you most likely have an older Pentium 4 processor.

JMICHAEL thanks for the info. Are you running this card on a 350 PSU? When i went on their web site it says you need 425 PSU at 28AMP.My Dell Dimension 8400 has a 350Watt PSU and 18Amps. Every card i want to use people are telling me my PSU is to low and it wont work on most cards. I wish i could use this card sounds like a good card. Please let me know for sure if i can use this. Thanks Alot

I used a superclocked EVGA 9600GT on my 350W PSU which is overclocked the same as the BFG to 675mhz without any issues.  However, my 350W PSU had 25 amps.  Your wattage is not a problem since the card only uses around 100 watts under load, but I'm not sure on the amps.  Mine stated 24 amps and a 400 watt power supply requirement.   The manufacturers always overstate what is really required as you do not draw anywhere near that power consumption.  Also, the specs they state is for the entire system not just the card itself.  Your entire system would use less than 200 watts with the 9600GT running under full load.  I consider the amp requirement to be more critical than the wattage requirement so it is hard to say if you will run into a problem.  You could consider one of the new green cards or energy efficient cards as they do not require as much power and do not even need the additional power cable from your power supply.  HERE is one to look at.  HERE is another and you can see the requirements are only a 350 watt power supply with 18 amps. 

Any Video Card will be held back by your cpu.

The Radeon HD4670 is what I would recommend.

http://www.insidehw.com/Reviews/Graphics-cards/ATi-Radeon-HD-4670-vs-nVIDIA-GeForce-9500GT/Page-3.html

JMICHAEL, The xfx card needs 400PSU. Do you know what card i can absolutley use in my pc without having to upgrade the PSU? I  have XFX GeForce 9500GT 1GB DDR2 in there now but it seems to bog down my PC. Would a GeForce 9500 GT 512MB DDR3 work better? Would their be any inprovment in my PC performance? Thanks

The 9500GT 512MB DDR3 would give better performance, but it would be only minor and not worth the upgrade.  I am not sure what you mean by your current 9500GT bogging down your computer.  I could understand the 9500GT getting bogged down by playing certain games, however.  The XFX card does not need a 400W PSU.  Your entire system with a 9500GT does not use more than around 175 watts and that is under load while playing a game.   The 9600GT's are fine and the HD 4670 mentioned by Speedstep is better than the 9500GT.  HERE is a list of HD 4670's and they will not use any more power than the 9500GT.  Unless your power supply is just going bad, you should not have any problems running these cards.  Again, they will just be bottlenecked by your older P4. 

There are so many of them im confused. Could you send me a link for the one i need to get? Thanks

JMICHAEL, Can i use this card

HIS Hightech H467QT512P Radeon HD 4670 IceQ Turbo 512MB 128-bit GDDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported

in my Dell Dimension 8400 any problems fitting it in? Thanks

The HIS is the most popular one at Newegg.  It is a dual slot card so you just need to make sure there is no other card in the PCI slot right below the PCI Express x16 slot.  Otherwise, it should fit fine.  I always just make sure I know the dimensions of the card and take a measurement inside, but I don't see an issue where it would not fit. 

I just read here this card has its own audio and will disable any audio on the motherboard.I have a audio card on my PC so what do i do about that? Thanks