My upgrades were based more on reliability than a certain rps/trigger response but my upgrades were; SHS 15tooth piston
also i picked up a sorbothane pad to help fix my Angle of Engagement but it varies for each rifle, also can help reduce shock.
and a lonex A1
as for the prometheus hopup chamber, i have one myself and it seemed a bit overpriced to me, id say hold off until your original hopup breaks or if you want to Rhop your rifle. I also had one of the Prometheus buckings and maybe it was just me but it was super tight in both of my hopup chambers, although everyone around here (me included) seem to love the g&g green buckings