Which CO2 or multi pump?

So I will have my main hunting rifle soon but in the process of buying a scope for it, I accidently bought a second scope on trademe.  I bid $41 on a new Gamo 4x32 scope (rrp $119), thinking that with almost 2 days to go and the previous high bid $40 it was bound to go higher but I was wrong.  I was mainly just seeing how the bidding on trademe worked as I hadn't bid before, oh well.

In any case I'm left with a 4x32 scope that I doubt will hold up to use on a springer long term, despite being air rated.  So that got me thinking, it might be good on a CO2 rifle like the Air chief rapid repeater, where recoil won't be an issue and shots would be fairly close so 4x would be plenty.  The use would be sparrows and starlings around the barn and thought the right CO2 or multi pump might be quieter than a gamo CF-S and would be more forgiving to shooting from various rests and different holds.

So I'm considering these (but open to recommendations):

Air chief rapid repeater .22 CO2

Crosman rifle 2250B .22 CO2

Crosman 1077 .177 CO2

Cannon 737.177 multipump

Cannon 737L (longer barrel) multipump

The cannon multipump looks great and is affordable and I believe more powerful than the CO2 rifles unmodified but I worry about its accuracy/consistency.

The air chief I would assume is the best of the CO2 options but a bit pricey for a low powered rifle.

I like the idea of the 1077 but don't know how accurate it is likely to be?

For those who have used one or more of these rifles, what are your thoughts? I value accuracy first, noise second and power (including ability to modify for more power) third.  I don't expect amazing quality from any of them but decent quality would be nice.