Yeah, I agree that you should be able to get a better price for a tank somewhere. Even brand new at my local fire extinguisher shop, a 5# is $60, and that's filled. And I don't even consider that bargain hunting - that's premium convenience and service.
I think you're on the right track w/ the regultor and Fabco needle valve.
But speaking of "premium" - GLA, wow. If you've got the money and don't have that DIY bug that a lot of us have (enjoy putting stuff together), then GLA might be the right choice.
I personally gleen a good bit of satisfaction from taking the reins, so to speak. Plus, you gain a good bit of knowledge about your equipment and are better suited to diagnose a problem when you've researched each individual part and assembled it yourself.
Lastly, I fully support the move to co2; just be ready - the cost is going to be maybe $50-$100 more than you think. All the sundries that you're not focusing on right now as you shop for the tank & regulator; drop checker, reactor/diffuser, timer, KH test kit, various connecting pieces and elbows if you're assembling yourself...