What should I upgrade my Tippmann A5 with if I want a light, accurate and long range marker?
Forget the Tippmann Flateline or even the Smart Parts Progressive. I would buy the BT Apex barrel system. IMHO, it is the better choice of the three. Lapco offers an inprovment over the standard BT Apex. They sell an Apex-ready Big Shot with an Apex tip for the same price as the Tippmann Flatline. Other A-5 barrel owner favorites are: Palmers Brass, Lapco Big Shot, and J&J Performance. 56/45000 is nice but the 68/4500 is IMHO a better size, especially if you are going to haul it around on your pack/waist using a harness. You can pick up a nice DXS 68/4500 for about $10 more than the Empire 56/4500. Either tank will fit in the NXe 4+1 Camo harness.