Get something with a gas ram / Nitro Piston. It is a huge upgrade - less noise, less vibration, wont take a set, and its not effected by temperature. I was skeptical at first, but now that I have one, I won't ever buy a break-action without one.
In .177 cal, look into the Gamo Whisper 'Royal' with a Nitro Piston. It should run you about $300 with nice wood, checkering, and a good finish. Of course it also has the integral noise reduction device and adjustable iron sights.
But for sheer power on game animals at any range, consider a 25 cal gun. I have been using a Walther Falcon 'Hunter' in 25 cal, with a Nitro Piston, and its power blew me away - I was still stuck in the mindset that airguns, especial single stroke guns, were weak... This gun will through-penetrate a #10 steel coffee can full of water at 10 yards and keep trucking with a 40gr pellet. It penetrated 18+ inches of water in my Fackler box, which is equivalent to 12+ inches of ballistic gelatin. The Walther runs about $300 as well.
The Walther Falcon is also available in .22 cal with a Nitro piston, and it boasts quite good velocity. It can do everything the 25 cal version can, and probably do so just as well. If you are stuck on a .22cal, then I wouldn't look any further unless you want a PCP or something.
You have several other nice options with old conventional springs as well, but those two would be my choices in your shoes with your budget.