The hassle you get for having a response trigger just isn't worth it. Lots of walk-ons won't allow them and you'll be pulled up by refs at big games all the time.
Go with an E-grip, JCS Duel Trigger, WAS board and QEV mod.
The LP kit does help with efficiency as does having a good reg.
I'd also recommend a JCS RVA, and a JCS gold powertube, and a Maddmann spring kit.
Barrels- well, your choice really. If you want good range, the Apex is the way to go. Want better accuracy? Go for any of the well known branded barrels that you like, Lapco Snapshot seems to be the barrel of choice amongst A-5 enthusiasts.
I'd also recommend you change the hopper over to an R5 from Ricochet
grips? well, you are out of luck. Unless you buy the replacement frame from JJ's , which will accpet numorous aftermarket grips, there isn't much choice. Hotshot paintball/ UMS sell a stick-on grip surface, similar to skateboard tops. Hogue make a pistol grip called the "HandAll" which, sort-of fits and Ergogrips also work.
hope that helps