Best option for using Logic Pro 9 live?

I am a guitarist and I have a really nice pedal board and amp but the problem is that my amp is sometimes too loud for some of the churches I play at so at my last booking I used my drummers 15inch pro and ran logic that virtualized my exact amp in Logic and I just ran my actual pedal board into the computer and then back out into the system and it sounded GREAT! Now my dilemma is that I have a 13inch Pro and the the multi I/O port for both line level in and out. What do you think would be my best option to run Logic pro live through my 13inch pro without getting any lag? Thanks