Benjamin ,ninja or air venturie ?

Welcome to the world of PCP! I would consider doing a little analysis. Since I don't know how big of tank you want I will just assume you don't care on the size. So..... First what is the $/cuft or $/cuin cost of the tank. The bigger the tank, usually the more economical the cost of the tank, or as they say the more "Bangs" for your tank. Pun intended. Now you need to consider what kind of valve, and what attachment options come with the tank. As an example AOA sells their Omega tanks with a DIN valve and a DIN connector-hose assy. I think they even include the quick disconnect female attachment to go on the end of the hose. Exactly what you need for a Marauder. So think about how you are going to fill the tank, and then how you are going to fill your gun from the tank and weigh in the total cost of all the attachments. Good luck!
 
1st off see if your local fire department or Paintball shop can fill a Airgun tank to 4500 psi.....
What I use for all my Marauders is a Air Venturi 90ci tank, being its already regulated at 2900psi I just attach it to the Airgun where as my Air Venturi 74cf tank I needed to buy a separate regulator and lines to hook it up for constant air and with that said for 550 you can get a 74cf tank and have it or the 90ci tank filled at a paintball shop or Firestation if they or you have the right adaptor then you can just use the tank to refill the gun when needed just have to be carful not to overfill the airguns airtank with the 74cf tank. I usually only fill my Marauders to 2800-2900 psi and that's what makes the air Venturi 90ci tank nice, it will only fill to 2900 psi no more which also makes it a nice little tank to tether to the Airgun or carry in the field in a backpack.
I also have the Air Venturi air compressor so I can fill my own tanks... If ya get a 90ci tank and think you are going to fill it with a hand pump good luck, been there done that and never again took forever,need to have a lot of time and muscles hahaha, it not a fun thing to do for what little air you get.