My opinions differ somewhat from the previous offerings.
As always, the gear you choose hinges on a variety of factors, one of the big ones being your experience and resulting preference and taste. The only way, in my mind, that you can truly develop a taste for these things is by giving them a good run and then making up your mind as to what makes a good piece of gear for your needs and what doesn't. For instance, a certain preamp may work fantastically for rock drums but may be too noisy for recording an orchestra. Furthermore, the difference between a seasoned pro and a novice is that the pro has years and years of experience in evaluating a variety of different pieces of gear and this comes from having the oppertunity to actually get their hands on them. Of course, there certainly isn't anything wrong with the preamps in your interface, just like there isn't necessarily anything wrong with your compressor plugins. It's just there is a certain aesthetic with analog devices and they often possess a certain musical "something" that is difficult to describe but works beautifully and sounds equally so. You also often have to pay an arm and leg for the ones that really shine.
Often knowing the difference comes from using a mediocre preamp, like a Behringer or a Mackie and then getting an opportunity to work with Neves, etc. Sometimes it take a whole project to come to fruition before you go, "ya know, those preamps worked GREAT on this stuff" because whether they're great or not often doesn't present itself immediately and that just comes down to the inherent subjectivity of recording. I guess you could also make mental notes along the way like, "X preamp worked great with X mic for X instrument that time so I'll try that again". There is nothing wrong with knowing a winning combination.
As far as industry standards go, there are the classics that are tried and tested: Neve 1073, Focusrite ISA, UA 601, API 312, etc. There are also a bazillion boutique options now available and if you're thinking about going into that world I'd say it's most cost effective to buy a 500 series rack and collect them that way. You'll save lots of cash but you can feasibly collect a variety of different specimens.
Just expect to pay around $600-$1000 a channel.
Of course, when it comes to value for money a good medium format console just can not be beaten for price/channel ratio. I personally use the preamps on my console for everything, which is a very common scenario for a lot of trench working stiffs. It's a Chilton (Calrec) CM2 and the preamps are stellar. It's all British, fully modular and is 100% discreet with 70dB of gain. I picked it up for around $360 and as far as I can tell, each MODULE is going for around $700 EACH. So, I scored since I have 10 channels making the console worth around $7000! Keep your eyes out and you can improve your situation pretty quickly for minimal investment.
On the topic of compression...
Do whatever sounds best. Don't be afraid to compress on the way in. I almost always do on bass and vocals but take in a case-by-case scenario. It's kind of seen as an old school approach these days because of all the post-rationalization that is available to us, and maybe it is, but if you have a good compressor unit that sounds good and you have the experience to make it work on input, then do it! Personally I'm sick of all the pussy-footing around input processing because I'm the tracking engineer, goddammit, and I'm going to fucking compress it if I see fit!!!!
Hope that helps.
Cheers