gtx3071 is about as big as I'd go on a stock block. I'd still prefer the 2867. if you're strapped for funds, get a K04 or BNRs1. If you want a nice little bolt on upgrade get a corksport/bnrs3/gtx2867. if you want to go big, get a bnrs4/3071 or something from borg or PTE.
Bear in mind, that with any upgrade to the turbo, you'll want to upgrade intake, dump (and rest of exhaust if you've got the $$), map sensor, boost controller, and tune (Accessport, Hypertech, Mazedit, others. Accessport is most popular). Not all of these upgrades are a necessity (you could run stock intake and stock dump for example) but they have to be removed to replace the turbo anyway, so you'll likely not pay installation costs, and there's not much point getting a bigger turbo and then making it asthmatic with the stock intake.
@Howard's advice is good, he was one of the main guys who helped me when I had to make the same decision as you.
2XS 3" intake | 3 Bar MAP Sensor | GTX2867r | 2XS 3" twin dump pipe | 3 port Grimmspeed EBCS | Cobb AP V2 | Purple Drank Tuned