Yo guitfreak! A preamp raises the level of a mic's output to line level so it can be recorded. All pres change the sound in the process, some more than others, and some more pleasantly than others, and what pleasant is, is often a matter of opinion. To a large extent, you get what you pay for.
Professional studios often use preamps that cost $1200 a channel or more. If a Behringer mixer costs $100 and has 10 preamps in it, how good do you think they are likely to be? Preamplification is more critical on some sources than others. In general, vocals and acoustic instruments call for the best available preamps, and sometimes percussion can sound just fine going through a mixer's preamps.
What kind of preamps you use depends on how many signals are being recorded simultaneously, your budget, and what kind of sound you're looking for. Generally, a good project studio should have 2 or more higher quality dedicated preamp channels, and a mixer/console for cases where more signals are being recorded (drums, live studio recording). I also prefer 2-channel preamps, because they are almost necessary for stereo recording, where matched pairs of mics are often used.
That said, I have no use for the ART pre you mentioned, nor have I heard any ART preamp that I would pay a dollar for. For cheap, find an M Audio DMP3. It's discontinued, but still available if you look around. If you're only recording up to 2 signals at one time, a 2 channel preamp, even a good cheap one, beats the hell out of most mixers. Note that there are some high end mixers, often called recording consoles, with really good preamps in them, and the sticker price may give you a heart attack.
Lastly, whether you go into the recorder/comp clean, or add EQ/FX first, depends on a couple of factors. The first is whether the presence of those effects affects how the recording artist plays. Many times, it makes sense to add the reverb or whatever to the headphone mix of the guitarist or singer, so they hear what they expect to and play normally, but you record it dry so you can add the FX you want later, or even re-amp the signal.
Also, it depends on the quality of your available outboard FX and plugins. Really good plugins are often better than cheap outboard boxes, and really good outboard boxes are generally better than any plugins that have yet been made available. That is changing, though, and plugins are getting better every day. The biggest advantage of recording dry tracks is that when you add FX/EQ/compression, and it sucks, you can remove the effects and try something else. If you go in wet, you better get it right the first time.-Richie
