Starkeeper, actually you don't need two soundcards if you can take the somewhat lower quality of an Audigy for both the accompaniment and the melody/lead voices. I needed the Audigy at first because there was no easy way to play styles with program changes. The soft synths are not very good at this. As a result, I used the Audigy for this and the M-Audio Audiophile for my lead/melody voices. It worked real good!!!
It is now about a year or so later and there are very good soft synths around that can accept program and effect changes from the style player, e.g., Project5 with LiveSynth Pro. I can rewire Project5 thru to Cubase SX launch Kontakt for my lead voices and DecaBuddy for my vocal harmonies. As a result, I really only need one soundcard. I have sold the M-Audio and purchased the Steinberg VSL2020. This soundcard is a step up from the Audiophile. Once I build my Shuttle Music Computer, I will likely go to one of the top RME soundcards.
In the meantime, I have kept my Audigy to serve as 2 Midi In/Output Ports as well as a mic input. The sound of the mic is sent thru to the VSL2020 for processing.
So the short and the long answer is you only need one soundcard. You can use the Audigy for most things including ASIO, WDM and GSIF drivers if you use the KX Project Drivers. You will find however that the so called professional cards give slightly better performance (Signal to Noise, dynamic range, frequency response, distortion, etc.).