hi there
In Regard to your question.
You can do As I do,
I use a Roland VS-880EX Digital Recorder and what I do is use the effects from it such as for vocals and guitar effects.
Heres my hook up:
I go from the RCA outs from my Roland to my Audigy 2 sound card in the Aux 2 in put.
Keep in mind that this will not allow you to control acid interface but will all you to use you Tascam as a mixer to get a cleaner in put sound, that way when you start to mix in acid using varaious effects and what not you have the best quality in put sound on that track as you can get.
You will have to do one track at a time unless everything is pre mixed already in your taskcam, I'm not to up to speed on you board and what it can do but mine is a digital recorder, so if I want to I can mix it there and just use one track in Acid and then drop it in sound forge for the Master Process.
Hope this helps and bit,
Ronnie Rokk