You seem to have a simular ideas on markers as i, but not quite the same set up.
My A-5 works well for me and dont see any reason to upgrade all that much.
std A-5 with 4500 p.s.i. H.P. 1.1 ltr fibre wrap tank and 14" DYE u/l barrel.
Its accurate and has a nice balance to it.
This set up has served me well for a few years and hope it will do for you if you choose to use it.
good luck