How serious are you about target shooting?
The last time I looked at the 2078 specs (many years ago), the accuracy spec was not very impressive.
That was unfortunate, as the rifle was priced very well for a starter rifle.
Contact Beeman about power options for the rifle. I think there is/was one, but I read that a long time ago.
Independent vendors may have made their own bulk co2 adapters.
If you are going to shoot a match, I would prefer bulk co2, which holds more co2. In other guns a bulk fill should/will get you through a match without the hassle of a gas refill in the middle of a match.
For bulk co2, you will need a co2 tank (I would limit to no more than a 5 pound tank, for ease of handling). I used to refill my bulk tank at a fire extinguisher service company.