Wow,
KBP, you've really limited your selections. None-the-less, I'll take a swing at making a couple of suggestions:
Walther Terrus (~$250)
Benjamin Trail Nitro Piston (~$270)
Hatsan 135 QE Vortex (~$300)
My Trail NP, however, is very picky about the ammo I feed it. So, be prepared to do some work if you get one.
I think the break-barrel design is not the best over the long term. As I see it, the main problem is that the rifle isn't solid because the barrel "breaks". For serious shooting, you'll want an optic of some sort and over time you'll find the barrel doesn't line up with the rest of the gun. Personally, I'd save up for a side- or under-lever. Then I'd save up and one day get myself a PCP rifle. The "Pre-Charged Pneumatic" (PCP) will require some way to fill its air reservoir. Do your research before making a purchase!
Otherwise, check out the Air Arms TX200 or the Walther LGU Varmint for a nice under-lever! Both are about $580-$600. But, they're VERY accurate without the need to carry equipment along to fill them when they get empty.
Enjoy!