selecting system

Hello everybody, I've worked for some time in robotics.But that'd been
some simple works. working with atmel's 8051 uc. (89s52), for line
tracking, odometry and motion control.

Now I'd like to concentrate on some kind of machine vision, say to
detect specific object , color etc.
Although we can use PC for the purpose, I'd like to have some uc or
processor embedded in robot. So which micro controller / processor
would be suitable for the this additional purpose of image processing.
PIC? AVR? ... and I suppose it must have sufficient speed and
powerful.

can I have the estimated cost for the over all system too?

Also it'd be great if I can know basics on which kind of cameras to
use, interfacing the camera i.e overall system. Having some experience
with VHDL, if FPGA could give the solution please advise me.

Waiting for your help!!!