1) I didn't quite well get your question.
2)You've got a dual core E4500, so it isn't ideal for gaming these days. If you're thinking of upgrading, then go for a good quad core CPU.
3) The GTX 460 would be bottleneck on that system and so it would not perform the way it's supposed to perform.
Get the GTS 450 instead.
4) Even if you've got DDR2 RAM, it DOES NOT
mean that it can't support a GDDR5 GPU. Honestly, why do they even call themselves as 'technicians' ? The RAM is a bit slow though, 667 MHz.
ALSO: Even if your PSU is a 450 W one, I don't think it's a good one since it might be the one that came with your PC cabinet. A GTS 450 requires a 6-pin Pci-e connector and therefore I'm not sure it will be able to run it.
If you are thinking of upgrading that PSU, then get a GTS 450. Otherwise, I'd get a Radeon HD 6670. It's the best performing card that doesn't require an external power connector. http://www.newegg.com/Product/Product.aspx?Item=N82E16814131440