Hi earlystart
Both my rifles are .177 they are tuned to between 11.6 - 11.8 ft/lb, with an 8.4 grain pellet this works out to be around 6.4 ft/lbs on impact at 50 yards.
With .22 using a 16 grain pellet it works out around 7.5 ft/lbs at 50 yards. Most air rifle hunting is usually between 20-40 yards.
For a head shot on a rabbit you need 4-5 ft/lbs on impact, so yes it is enough.
If you are looking for a springer I would recommend the HW97 or an HW77.