That's great to hear! I just got my A5 literally last week and I have to say that I'm happy with what I have. As far as regarding the Tippmanns not being consistent. I would have to agree; however, that goes with any marker. It depends on a number of things: paint, the airsystem being used, the upgrades as well as the cleanliness of the marker and proper maintaining of it. So that being said, any marker can be inconsistent from a various number of things. Aside from that, I have seen that my A5 was a bit inconsistent due to using CO2 and the paint I had at the time. After upgrading to better paint and using a high pressure N2 tank I have definitely seen better consistency.
Now moving onto your barrel. Basically you'd want to stay with anything that's under 16" in length. A 16" is good for poking through brush and pushing against bunkers. While 14" and below are good for compactness and ease of portability within your gear bag as well as cleaning if you don't have a big enough squeegee. Now those are just broad generalities. Going onto which barrel. That's up to you on how much you're willing to spend. Definitely don't go with a barrel kit because to me that's a waste of money. Just do what the pro's do and overbore. Ex. paint size is .689 and below these days -- get a .689-.691 barrel. You will be set for a long time not having to worry on which paint to get and worry about getting barrel breaks. Some individuals, like me, for instance get the Flatline barrel. Reason why? It's exclusively for Tippmanns. So basically, in a sense, getting a Tippmann for the sole reason of the Flatline makes perfect sense. Because it's one of the few barrels that actually make the paintball travel farther. That to me is why I will only have a Flatline on my A5. If you absolutely need a suggestion for a barrel then a good inexpensive one would be the Proto 1-piece. Some others include Smart-Parts 1-piece barrels and Custom Products. There are many others but I'll save that for other users to prey upon
Anyway I hope this helps,