Which is better, AGP8X or PCI ?

A 400w PSU is fine for a 9500GT but that's not a good gaming card, older games perhaps (pre 2005) but not the newer ones. Your PC only has PCI and an AGP slot though and I don't think the 9500GT is available in PCI.

Only if its a good PSU. There are a some over rated PSUs on the market which advertise 400+ watts but really only 250 W. Try for a good brand PSU or one that has good reviews on a respectable website.

If you only have AGP you might as well use AGP. The 4650 is probably the best AGP card you'll find these days.

AGP is by far better, but still obsolete.

you would get much better games performance for the money by getting a budget PC or saving for a little while.

The biggest bottleneck you face is that P4.
If you install an AGP card, its still gonna be too slow for games.
You can build something much, much faster for $400-$500.

I had a similar problem with a Pentium D machine a while ago.
Ended up with a cheap Mobo, pentium dual core E5300 and an ATI 4350, 2GB RAM. The difference was phenominal.

^ what he said.

If not the 4650 agp version might do the trick. Are there any 9500gt on agp?

If you Upgrade the PSU, be careful about the power to the motherboard. The connectors changed.

No, I don't even think there was a PCI version.

No PCI or AGP for 9500 GT but I would do a cheap overhaul like new motherboard, CPU, GPU, case, and PSU and if you want a new graphics card I would get an AGP card and if you like nVidia I would get a GeForce 7 series as that is the last of the nVidia cards to support AGP.

PCI-E
AGP
PCI
ISA

Thats the order you should be looking for cards, if your board doesnt support PCI-E, then AGP is next in line of terms for performance, and so on.. AGp's are old technology and is very hard to come by a decent powerful one, even the old ones werent all that performance crazy. Going for BIG bucks now though, even 2nd hand (UK based)

Thanks for your response. Really appriciate your time.