Re: Sooooooo....
Mercuri said:
However, I've also noticed that if I only record ONE track and don't mix it in with anything else, it sounds a HELL of a lot like "that sound". . . .
B) Maybe some of us ARE achieving 'that sound' in our recordings. However, when we don't mix through a fantastic console that is sophisticated enough to maintain 'that sound' through the mixing process, it ruins it. It degrades it (or preserves, it in the case of digital, maybe?) in a a way that is unacceptable to the human ear - that little thing that makes you cringe when you hear your mixes and they just don't sound right. The individual tracks sound OK, but not the mix.
You see, now you're starting to get warmer here. I think your next step will be your biggest eye opener yet, and hopefully will open things right up for you.
The reason your mixes aren't retaining "that sound" throughout the entire process is
because of the very fact that your individual tracks sound "close," as you put it, in solo mode.
What the f*&% says Mercuri to Chessrock? I'm not sure how much you already know, so I apologize if I'm stating the obvious to you . . . but the idea is to get the tracks to interact with one another from both a dynamic and sonic/tonal perspective. Your tracks no longer exist in a vaccum at this stage, so you can't treat them like solo instruments. Don't expect that getting a great mix is to get everything to sound brilliant on it's own and them just mix it together and it will all sound brilliant together. In a perfectly logical world, that would be the case, I know, but audio is a funny beast.
Example: I might start to sing a song, and I might sound great . . . on a good day, mind you, and after you've likely consumed some mind-altering substances. But I might sound great. Then, let's say Littledog were to start singing with me, brilliantly and flawlessly, but in a different key. Now suppose Pipeline added his vocal prowess to the mix, yet in a totally different key still.
It's very likely we'll all sound brilliant on our own, but if you mix us together, it will probably sound like a train wreck.

Not the best example, but it's an illustration, nonetheless. The idea is to get us all to blend with one another, tonally and dynamically.
Now if each one of us were properly blending with one another, chances are we'd sound like shit in solo mode. Ever try listening to you or your friend's harmony track in solo mode?

It can be a real gut-bustingly comical experience, and I highly recomend it, under proper conditions. The better it blends with everything else, the funnier it will likely sound on it's own.
Anyway, this is getting in to an area that has A LOT more to do with the knowlege aspect and a lot less to do with the technology. This is also where a lot of folks make the mistake of assuming it's "a gear thing" and subsequently throw a lot of money at it in a futile attempt to circumvent the inevitable learning process.
There are no shortcuts at this juncture. You're going to have to crack the books and get studying. If you don't have a thorough knowlege of the various frequency ranges, then it's time to get crackin'.
Pop Quiz: Do you know what frequency ranges can potentially be trouble when mixing bass guitar and kick? Are you aware that the accoustic guitar, if left alone, is one of your bassiest instruments and will likely compete / clash with even the bass guitar and kick drum?
Do you know what frequency ranges to focus on for each track when using EQ? Do you know how to use a specral analyzer? What do you know about multiband compression, and do you know how to use it effectively to solve some of these issues?
If your anser to any of these questions is "no," or vague, then chances are it's time to hit the books, enlist at full sail, or whatever it is you gotta' do . . . but understand that at this juncture about 5% of the issue is a gear thing, and the other 95% is a brain (and ear) thing.