well, new turbos wouldnt hurt relialibility.. you could look into K04 turbos which would probably give a pretty sizable hp boost... this isnt a cheep mod tho... upgraded turbos are stronger and built better than stock...
check out MTM's stage 4 upgrade... they only make it for the 6speed 2.7Ts though... (because the tip trans cant handle the added hp). Check it out though, itll give you some idead. Joe Hoppen Motorsport has awesome MTM
2.7T Stage 1, 2 and 4 upgrades, as well as other good stuff for your car.