I would reccomend the Combat BT-16 barrel kit. It's extremely accurate and gives your gun a sniper look. It also has a sight which makes you even more accurate. Apex barrels are VERY handy, but they're not actually barrels. They are equipment pieces ...
You need to get barrel's that are threaded for the A5/X7.... so here are some... and my favorite..... the best for it's buck is the CP, custom products barrel.... I have been playing 5 years used over 2 dozen barrels and own 12, I have 3 CP's.... the...
Last time I checked which i've had tippmann model 98s since they came out I don't remember them coming with regulators. That would be an aftermarket upgrade which you'll be just fine without one unless you are wanting to seriously over haul your tipp...