"Discretion is the better part of valour"
Rather than spend a loada cash on a highly expensive soundcard/interface, if you want something portable with at least eight or so inputs get hold of a digital porta-studio like the Fostex VF-16 or VF60 - although the audio is only 16-bit (CD quality) something like this will be easy to use, cheap, highly portable and adequate for your purposes - you'll be able to transfer all tracks as wavs to your PC afterwards using the optical input on a basic semi-pro soundcard. I have recorded bands in live situations this way using pre-fader sends from the front-of-house desk (in larger venues), although I understand that most churches will have a simple PA setup. If your sound guy has a decent desk you'll be able to set up two sets of signals - one for the PA and one for recording (Aux send/insert/direct record-ask the dude) or you can use your own mixer. I find this easier for live recording than moving a PC about (aargh), and the cost of the portable HD recorder and budget card (eg.
E-MU 0404) won't exceed that of a swish interface. If, however, you intend to expand your PC system into a fully-integrated pro-studio setup above and beyond the immediate task of recording church concerts, consider a high-end soundcard/interface (RME Hammerfall etc) instead. Better yet, install a multi-track open-reel tape machine in your local church and record on the most stable (& best-sounding) format ever invented!
By the way, using a mixture of both desk output signals and an additional stereo pair of condenser mics out front will help capture not only an accurate mix but audience reaction/hall ambience. Sometimes "dry" signal feeds sound a bit dead in a live context, although vital to overall mix balance. Be sure to check for phase coherency, though, when using combined signals (especially drums, if they are used). I use waves PAZ analyzer for this purpose, as well as for checking even frequency response. If combined signals cause phase probs ("swishy-phasey-sounds") alternative mic placement is preferable to resorting to drastic phase-reversal switching (your church PA system probably doesn't have this facility anyway). If you have a good-sounding space (most churches are naturally acoustically reverberant), I say use it!
Ideally, you'll want to capture the "feel" of the live performance above all (especially in this context), and so a discrete, easily-operable, flexible and portable way of achieving this result is surely preferable!
Good luck in your endeavors!
Ali.