is my asus p5e-vm hdmi mb too old to work with EITHER the evga 750 ti or radeon 260x? if it is which gpu should i look into for that mb?Depends on the CPU you are using... if you have a Core 2 Quad then I'd say that its an ok pairing; however obviously a new build would probably be better. If you have a Core 2 duo or lesser of a CPU then the CPU would be a serious BOTTLENECK for the GPU.

What CPU are you using?
How much RAM and RAM specs?
What OS are you using and version?cpu - q9450
ram - 6ram
windows 7 professional
pioneer dvd drive
80PLUS Certified EarthWatts 380W power supply(came with antec case 2480 years ago)
250gb seagate+1tb seagate
Anker® Uspeed USB 3.0 4-Port PCI-E Express Card
1 big fan unerneath dvd drive(front of case)
1 big fan  back of pcThose video cards will work on this system; however because the motherboard is not PCI Express 3.0, and might not even be 2.0, its probably 1.1 or 1.0 and so you can find yourself bottlenecked by BUS saturation. Only way around this is to replace the motherboard with one that is 2.0 or 3.0 to have more BUS bandwidth to support the data of the better video card.

I'd buy one of the cards as an upgrade and see if its ok for you. If it isnt you likely were going to be buying the video card for a newer build anyways and so its not a waste of money.

I have run 3.0 videocards on 2.0 and 1.1 PCI Express 16X slots and they work ok for the games that I play. Most video cards are backwards compatible from 3.0 to 2.0, 1.1, and 1.0

I have a 2009 motherboard that is PCI Express 1.1 and I have a 3.0 card in it and I am getting 60FPS PLAYING most of my games at normal graphics settings but games I play are like Tera Rising, World of Warcraft, Rift, Diablo III, Skyrim, GTA SA, Driver Parallel Lines, Need For Speed Carbon, and Flatout 2.

I DOUBT you'd find bus saturation to be much of an issue, you'd be bottlenecked by your CPU before reaching the limits of PCI-E v1.  I agree though that either card would be fine for your system, I don't see any issues with that.