depends of course on what you need it for!.....I dont usually like to compress going in (I'll use plugs later as needed) I like keeping my options open and restrain from squashing things.
for me I use a simple FMR RNC in the "Super Nice" mode which is very transparent and just takes the top off my vocals (mainly) and anything else I decide to run it through....it goes for about $150.00
i too would rather not compress on the way in--i usually only do minor peak limiting on the way in.
i have an rnc and i also find it useful in just about any role. it's a little slow for snare, though.
i've also got a symetrix 425 that i'll use for bass, kick, snare, guitar or anything else i want to throw through it. it does a pretty decent job and has a different character than the rnc.
i've also got a symetrix 528 (old version) that's intended for use as a vocal channel. it also kicks ass on snare, and isn't too shabby on guitar mics, either.
lastly is an ashly cl150 (i think), and it's in the guitar rig. it could be used as an insert on a mic'd amp, but i like it better in the guitarist's signal path (pre amplifier) to level out the playing some.
if you're looking for "the best under" a certain price level, check out the RNC.
When I use outboard units for compression, i use units that purposely colour the sound; thus I commit early in these circumstances to what the track is going to sound like. A valuable thing i have learned on this BBS is that there are some very good 'coloured' compressor options available for little money. Among them, the symetrix 501, and the dbx 119 are the units i have experience with so far. Great compression with colour (ranges from mild to heavy) for under a hundred bucks each..hard to go wrong with one of those!
Check out the Empirical Labs Distressor. They're great. Also, UA 1176, LA2A, SSL FXG 382, Alan Smart C2. There's a good LA2A clone too, the Red Stripe. And for under 1000 bucks about the only thing I personally recommed would be an FMR Audio RNC pair for certain applications.
Here's another vote for the RNC. Sure, you'll get better, like the Distressor, LA2A, 1176, Buzz SOC1.1, etc. etc., but the RNC does sit quite comfortable in a lot of pro studios. So for the cost, it a whole lotta bang for your buck.