Nope, an OC'd 7800GT is just barely a few steps in performance away from a 7800GTX. And now it's more like paying twice as much for a few more FPS, definitely not worth it.
Your better off looking at a OEM X1900XT if you want great performance for value (still expensive but awesome video card), or wait for the 7900GT and 7900GTX (most likely still not worth it but who knows only time will tell).