which GTX should i get?

im i need a nvidia GPU because ATI just isent compatible with my internal ATI for my eGPU build, and is giving me problems. so i need to buy a nvidia GPU but i still dont know which one..... the requirements is that it has to be either a 400 series or 500 series. and the GPU is going to be running at PCI 2.0 x1 (maybe x2 speeds if i get another cable or do some other mods) any suggestions? my system specs are:

intel core i5 560m @ 3.2ghz
6gb of RAM (will upgrade to 8 soon)
and i will be running at 1600x900 resolution.
i dont want to spend more then $100 on ebay.

the games im playing are

cod MW2, Black ops, world at war
test drive unlimited 2
BFBC 2
Battlefield 3
farcry 3
dirt 3


those are my most demanding games.

i know my limitation is the bandwidth speed at pci 2.0 x1 (x2), so with that in mind, i know i wont be able to play all games at max settings 1600x900 but still. ive seen someone play crisis 2 on 1080p with all ultra settings at pci 1.0 x1 speeds and get a playable 20-40FPS. he was using a GTX 560ti

same with BF 3 except 1280x720

[eGPU x1.1Opt External Screen] Battlefield 3 - YouTube

Here is a good link that solarstarshines posted in another vid car thread. Review it on cards you are looking at. By the way I have followed your progress, good luck.

Video Card Comparison - GPUReview.com

This could be a good choice

http://www.gpureview.com/GeForce-GTX-465-card-631.html

The reviews there don't look good(just 2) but I have a friend who uses it and it performs good for him

Your friends 560ti would be a good choice too, you mentioned 4 and 5 series but I would encourage you to look at this card too


http://www.hardocp.com/article/2013/...w#.UVMethxwqNp

Yeah that sounds good for your needs, Good Luck!!