I think the M-OneXL is the best in class at ~ $400.00. I use one of these myself. It blows away the lower end stuff (2-300) and hangs well with the more expensive stuff for live reverb and delay.
I do like the Lexicon stuff too (MPX500/550), but it is more of an airy reverb while the M-One is more "warm".
If you are thinking more money than that, then the PCM's are incredible.