I own
the 2408mkIII and think it is pretty good, as far as converters go in it's price range. It is obviously not as good as some of the high end stuff out there, but for me it is perfect. It has lots of options, 8 channels of analogue and 24 channels of ADAT or T/DIF....which would hook up directly to your behringer mixer (I think), and then into the computer.
If you do this, your behringer will be doing the AD conversion, so as far as "improving" the quality of your recordings, getting a 2408 wont be what you are looking for.
Maybe you would be better of buying something like
the 828 MkII. This has 2 onboard preamps, so you can hook your mic directly to this, and then straight onto the computer. It also comes with a Audio Only version of Digital Performer.....which will be fine for multi-tracking.
I think it even has ADAT I/O so you can bounce stuff straight off the behringer into the computer digitally, if you want to use the behringer converters.
If you want to buy a computer, for multi-tracking, or burning CD's as you put it, then either the 2408 or 828 would be usefull to you.....but wont seriously improve the quality of your recordings. If you want to achieve this, you would need to buy a really good mic, high-end preamp, and then record in a nice space. I just bought this old analogue desk and since using the pre-amps on it, the quality of my recordings has shot through the roof. Now if only I could afford a decent mic.......
Good luck mate!