the 357 might be a tad much for squirrels, but the big bore airgun stuff is cool. I doubt i will ever own one but you never know.

You might want to check out yellow network or gateway airguns for airgun talk, bunch of guys on there who know their stuff.

I just recently bought a benjamin discovery in 22 that i absolutely love, awesome accuracy and plenty of killing power on small game. Its a pcp gun, which you pump up, and it makes an excellent entry level pcp gun (got mine ordered thru walmart at xmas time for 299, that included the pump(which runs you about $150 new).

You can get a nice spring or piston rifle for your price range, but now that ive gotten into pcp's i dont think ill ever buy another spring loaded gun again.