Hey! Congrats on the rig! I just bought one as well!
As far as a battery goes, I don't think that the battery that comes with the system will power the laptop for an entire show. You can go the 12V way, the Valance way, or do what I did...bought a few extra Li-Ion batteries.
I use the VxPocket V2 sound card. You can use an M-Box or a UA-5 as well. Make sure you get 24 bits out of the interface.