lol i wouldn't say so...imagine a video card running on a USB port... ouch... No AGP or the new PCI Express is the only way i'm afraid
...unless lol... you could try getting a longer cable that will connect to both sides and then keeping it on top of the computer or something... lol j/k j/k.
Why do you want an external one anyways? Easier to set up?
Hope i can help
Kage