Soundcard confusion from Dell

I bought Dell Dimension E520 with no speakers, but with Sound Blaster Audigy Advanced MB software (I thought I was ordering audigy card but dell is sneaky). It has Sigmatel High Definition Audio Codec sound card. I have Boston Digital BA735 speakers that I used with my old computer (Gateway, Sound Blaster Live! video card). My BA735 speakers dont work with the new Dell's sigmatel because they require digital output and sigmatel only gives analog output.

Now I am considering taking my old Gateway's sound blasater Live! card using it to replace my Sigmatel on the Dell.

My two concerns are: Is this going to make my audigy software obsolete and am I going to run into any problems I havent forseen that you techies surely will

Thanks so much for any help