*Considering* Upgrading to HPA

Hi everyone, as the topic says, I am currently thinking of upgrading to an HPA tank. however I have a couple questions.

I know the rule of thumb for how many shots you get for HPA is the number of In.^3 X 10 or 15 depending upon 3k or 4.5k PSI. However, is this general rule going to help true for an A-5? the reason I ask is the A-5 uses a generious portion of gas, and also requires a high output, so at what point would I run low on gas? You can't really say there is a general rule for how much you can get out of a tank. Each marker is different, an a5 depending what you have on it like qev, rt stuff like that you will get less. I would say a 68/45 you should get about 1000 rounds. And you run low at the same point you run out at co2 which normally your cyclone turns off around 300psi

Also, I run a remote so the weight of the tank does not really matter much to me, and I dont want to spend an arm and a leg getting a tank. The reason I say this is that I know a steel 3k tank will cost much less than a fiber 4.5k, so would you guys say its a good idea for me to get just a 3k steel tank? You will get much less air out of a 3k, and you might need to buy a new remote if its not a nitro remote. (I'm not sure if there is a difference in those remotes but I would do it just to be sure)

Finally, what size/brand would you all suggest? again remember I run remote and dont care much about the weight of the tank, I just want to know what you all would say is the best deal in terms of what I would need. Go for a 68/45 or higher get a Crossfire or PMI pretty cheap and really good regulators

thank you for any help or suggestions you can provide