#1. Get a nice barrel. Dye ULs and CP makes some very nice barrels. The Dyes are more expensive though.
#2. Get a 14 inch. The whole more length = more accuracy and range is not true. The flatline does have longer range, but decreased accuracy.
#3. Get a barrel to suit your paint size. A $20 barrel will shoot better than a $100 barrel if the paint fits the barrel better. Freaks do well with this, although they cost alot to get differ bore sizes and whatnot.
#4. DO NOT GET AN ION!!!!! Yes they are ok guns, but you need to spend ALOT OF MONEY upgrading them so they work ok. If you buy one, you would need a new: Board, trigger, reg, barrel, feedneck, and asa. Thats around $150-$200 upgrading. Get a proto or mini.