My first WRT54G (one of the original Linux ones) died on me and was replaced by a WRT54GL. I would have never replaced it with another Linksys router were it not able to take 3rd party firmware.

If you just want something cheap just buy whatever you find at the lowest price. They should all work reasonably well. But my suggestion would be to get the WRT54GL and put the Tomato firmware on it. You don't need to make any further adjustments beyond the few you would make to the stock firmware. It's just a better performing system with a much easier to use UI.