It's a tough call . . .
I think my dream team would be a Soundcraft board with an RNC. That would give you about 4 solid preamps to play with, exceptional eq for the price, and a pro-quality compressor.
That combo might set you back more to the $700 range, though.
Almost forgot about the Symetrix, though. I'd almost be inclined to say
the Symetrix 528 would be a solid choice for all three. And the beauty of it all is when you're ready to step it up a notch, you can send it to audio upgrades (
www.audioupgrades.com) and have them beef up the preamp section.
You may even find that you're happy with the compressor. But if not, you can always bypass that in favor of the RNC, and still stay within the $500-$600 price range when all is said and done (ebay prices, that is).
Two more possibilities for ya:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=850576286
http://www.sweetwater.com/store/detail.php?itemid=EnVoice
Although I'm not sure if that's the best price you can get on the Envoice. My only problem with the dbx silver series is with the eq. It is a great deal, though, when you consider the a/d conversion is a step up from most, and the limiter is very good - comes in handy if you're recording digitally.
The Joemeek is solid. I love the sound, but the risk you're taking is that you might not like it. I do, but I certainly wouldn't want to use it on ALL of my tracks. And like I mentioned, the compressor sounds VERY cool - but it really is only good for four things: "too punchy," "way too punchy," "Whoa! Easy now," and too often "CLIP!" It isn't capable of limiting, which can be a neussance when recording digitally. It's awesome as an effect, but it doesn't exactly "compress" if you know what I'm saying.