Stacks are stupid.  

i think stacks can be pretty cool if they are low key-ish. like if they mostly are below the cab and are not chrome, i think they are sick. i would go with just a single 8" stack. besides, if you do sled pulls and things like that, your exhaust has to either exit straight up or down. and its harder to rip off on the trails. but i would keep the stock exhaust location over stacks any day.