Yeah, the audigy only has one audio input and it really isn't designed as a recording interface. It does what it was designed to do fairly well which is playback...you need something with more gazintas. The problem is, there's a lot of options. Do you want to record to the PC? If so, do you want to go PCI, Firewire or USB (yuck...USB).
There are a number of manufacturers and many types of audio interfaces, and these days, there are a lot of reasonably priced strong performers.
You can go PCI which is a plug in card much like your Audigy. Some say Firewire is the way to go but I think most will agree that USB simply isn't the way to go. IMHO, PCI is still viable which can get you a lot of inputs with good performance at a very nice price. Others suggest that PCI is on the way out and that Firewire will become the next standard. To each their own.
There are lots of manufacturers, one of my favorites is M-Audiohttp://www.m-audio.com/index.php?do=products.list&ID=pciinterfaces . Their driver support is very good and their performance in the market has been strong.
Read the forums, search for audio interface, surf the Musician's Friend website
http://www.musiciansfriend.com/navi...ording-cards-audio-interfaces?N=100001+304891 for a better idea of what's out there then when you've got it narrowed down to a few options, check back here for opinions on the device(s) you're thinking about.
Good luck