Question about Digitech vocalist Live 2/4

[DSS]

Hey all!!!
I am looking into getting something along the lines of the Digitech vocalist 2 or 4. I play live in a band but want to have something that I can use in my studio.
I see the guitar runs through the unit as does the mic.
Question 1 would be, can it work for vocals if there is no guitar at that part? It says it puts the harmonies in the correct key but if it doesnt have the guitar to help it will it not work during those parts?

Does anyone have any experience in this unit like this that has used it for live and for recording? Or a similar type unit in the same price range? $ 300-350?
Any help would be greatly appreciated since my local store sales people are not very knowledgeable on it. I have also read about it on many sales type sites that say the same thing over and over.

Thanks!

[cyealir]

I Have The Digi 2 And It Is Really Simple. It Has To Have A Guitar Signal However. I Am In The Process Of Upgrading To The 4 For The Versatility. The 2 Has Served Me Well. You Will Be Blown Away By The Sound And Simplicity Of The 2. I Am A Single Act And People Are In Shock When They Hear The Richness Of The Harmonies. The Trick Is Not Overusing It...hope This Helps