Meh, decent analog outboard is nice for those who can afford it, but by decent you're talking the kind of vintage/boutique gear found in top studios that sets you back thousands per unit.
Apart from some reasonable standalone preamps at the cheaper end of the spectrum, the kind of rack units in the price-range that most of us home-recordists will be looking it will be nothing to shout about, i.e. budget gates, compressors, EQs, etc that are more suited for live work and which will in no way be worth using instead of plugins within your DAW. All the Behringer composers, Alesis 3630, cheap DBX offerings, etc... not worth the money one bit, and only ever really seen in home-studios where stubborn people refuse to use computers to record with!
Same with reverbs - you'll pay over the odds to get an outboard digital reverb unit that is as versatile and high-quality as a decent plugin. Even the top top studios are now turning to good reverb plugins (e.g. Altiverb,
SIR2) instead of the units they used to rely on before computers took over. Affordable plugin versions of some sought-after digital reverbs (e.g. the top Lexicon offerings) have been made anyway. Probably the only thing better than a good convolution reverb is a proper echo chamber or real plate reverb (though you have to question whether the 'benefits' are worth the much more restricted versatility and huge cost).
So what is the point I'm trying to get to?
Save your money, buy a UAD card and invest in a few extra plugs for it. That will give you far more mileage than some cheap rack units. Why spend $200 on a cheap compressor when you can spend that on something much nicer from uaudio.com like the Fairchild emulation and be able to say '
zomg, I can has 10 of teh $40000 compressors running in my computerz + they sound r8 good'
Though that aside, you could still greatly improve your mixes with no more investment at all. To a certain extent its more about how you use your tools effectively and less about what those tools are. For example, a nice analog EQ is good if you can use it well and maybe know how to exploit some of its 'character', but its probably not going to 'add' as much to the overall sound as many people would have you think and you're not going to get anyone listening to your music on their iPod headphones and thinking "cool, that snare is going through a Neve 1073".
A crap engineer in a room full of amazing gear is still going to chuck out a crap result, whereas a decent engineer has the skills to make the most out of everything. The #1 song 'The Fear' from Lilly Allen's recent triple-platinum selling album was recorded and mixed almost entirely within Logic using all the stock logic plugins (including its bundled amp sim)... yet some people get Logic, don't produce very good mixes and think that is something to do with Logic or their gear that is hindering them. Just a thought