I think The Hit Factory has a faily decent EMT plate, that I'm sure they must really be embarrassed to have around in this digital age. Try calling them and see if you can have it for $500...
For under $500, I would say the Sony DSP-V55 is my pick if you want lush spatial verbs that sounds almost as good as the higher end Lexicon PCM processors.. Although it is a 20 bit dsp, it runs internally on a 52 bit engine which is still ahead of its time. Some people get all caught up in the 20bit/24 bit performance issue, and to be honest, I doubt most people could even tell the difference - especially once the track is mixed down. The DSP-V55 is very easy to navigate and intuitive and it has a pretty decent pitch shifter and doubler for the guitar heads out there. It also some very nice effects for live vocal performance without a lot of graininess (nice rolloff on the verb).
As far as the Digitech s200, forget it. I have one and the gain input and power switch is on the back (what was Digitech thinking?), but that's okay if get some gardener's kneedpads to crawl around the back of your rack with a flashlight).I found one cheap on Ebay ($52 plus shipping - a steal so I'll find some use for it). Sounds overproccessed and you better reduce the gains on the presets and save them to user programs or you will piss off your bandmates when you dial up new patches without turning down the volume first of your mains.
Just wanted to add that if you look around, you can get a Sony DPS-V55 for around $200 which is what I paid for mine. For $200, you simply can't beat it for professional sounding reverb.
on the lexicon thing i have used both the mpx500 and the mpx1 and i do prefer the sound on the mpx1. They both have the same dsp chip for the reverb but the mpx1 has a chip for effects aswell.
Although my pcm 60 smokes both of them ( somewhat going against what Bluebear said) cos i don't think its even full bandwidth. in fact i'd go as far as saying its way better than lexiverb and the pcm91.