Maine oxy on the 28 bypass if you tank is carbon fiber its $28 bucks.. they ship it out to Maine and you will have it the fallowing week. I know cuz i just did it last week my bros tank will be here Thursday. 603-627-7904 heres the number you have to do 603 if not it will go to the Maine location.
Personally I think it depends on the condition of your tank. If it need repair or you would like to upgrade your reg send it into that tanks company (ex. crossfire = crossfire) they will give you some great deals. I know off the top of my head is for a hydro test and reg swap its $60 plus shipping. If the tanks in good condition and you just want a quick hydro take it somewhere local. Some idea's are your fields store, a shop dealing with fire extinguishers, or diving shop can most likely take care of you. If you get it done local its usually $25-$35. If you send it out its $30+ what ever you want changed and then shipping which is $8-$12 per tank.
__________________ "One shot, one kill but then again everyone likes to see the bonus ball!"