Eyes on or off, the gun will only be able to shoot 25bps (The Humphrey HEA10A5-GL 101w is mechanicaly capped at 25cps).
There really is no best upgrade to get right away. It's all what you want.
Say you want better effeciency, get a new valve.
Say you want better consistancy, get a new HPR or LPR
Better accuracy, new barrel.
Here's a little(big) list that can help you.
valve - paintballtrader.com, eBay.com, b/s/t
lpr - paintballtrader.com, zenitram-mfg.com, b/s/t
hpr - any site or store dedicated to paintball
trigger - acidcustoms.com, paintballtrader.com, b/s/t
90* trigger frame - acidcustoms.com
hammer/ram - icdunderground.com, acidcustom.com, b/s/t
bolt - acidcustom.com, shocktech.com, paintballtrader.com,
www.freewebs.com/dementedproducts
grips - any site or store dedicated to paintball
harness - madpooh, sir stunnalot, b/s/t
feedneck - paintballtrader.com, *************.com, bradyspaintball.com, chipleymachine.com, b/s/t (bushmaster/freestyle threads!!! ion/impy will work, but you risk strippign the threads)
board - buynox.com, paintballtrader.com, b/s/t
barrel - any site or store dedicated to paintball
pull pin - eBay.com, blueforkdesign.us, w.freewebs.com/dementedproducts, b/s/t
guage - any site or store dedicated to paintball
'noids - airsoldier.com