I got my apex 2 from just paintball.
The difference in price is marginal between apex 1&2 so i just got the apex 2.
You can get them in 14 or 18" or buy the tip alone to fit to compatible barrels.
I went for the 14" to keep it small.
have you stopped to think why you want 16+ inch barrel? the longer barrel length does not increase the distance in the way you are looking for because once the paintball reaches 300fps inside your barrel its going to travel the same distance as soon as it leaves the end and it will slow down and fall at the same rate as any other barrel.
only apex/flatline will significantly increase distance because it gives it backspin and so it has a slight upwards force on it to allow a little more distance. however because the paintball is spinning it is less likely to break on impact.
long story short normal 18" barrel = 4 inches more distance than normal 14" barrel