Yo offpiste! Welcome to the board! It doesn't matter where in the signal chain the signal is converted to digital. What matters is that there can be no unit after that point that won't accept a digital signal. What also matters is how good the A-D converter is, wherever it is. If you're using a digital mixer or preamp, the soundcard has to accept S/PDIF or AES/EBU, depending on how you're putting out the signal. A really good soundcard with S/PDIF in is better than a cheap digital mixer, but a good digital mixer is better than a cheap soundcard.
Whever that conversion point is, the more it costs, the better it is likely to be. Most preamps with digital out also have analog outs, so you can send an analog signal to the analog in on the soundcard, or a digital signal to a S/PDIF enabled soundcard. Having digital out doesn't mean a high end preamp, and in fact some of the finest pramps money can buy are analog only. Also, some rackmount A-D converters cost thousands of dollars, and that's all they do!
I use a couple of digital preamps to bypass the A-D converters in
my Roland VS1824CD because they aren't that good. The weirdest version is piggybacking
an Avalon AD2022, which meets anybody's definition of a high-end analog preamp, into a DBX386, which is by no means high-end, then to the Roland. In this case I'm using the Avalon for it's great supply of good clean gain, and the DBX for its A-D converter, so the Roland's A-D (or preamps) can't mess up the perfectly good sound my Avalon made. Hope this helps in some way. Just remember, how much noise you have is much more a function of the quality of every component in the signal chain (including cables), and how they're used, than it is a function of whether it's digital or analog.
BTW, you can also toss out the concept that analog gear somehow produces a "warmer" or "fuller" sound. High quality gear used properly creates good sound, usually what the experienced engineer using it wants.-Richie
