Few of my recommended choices for under $600:
1)CZ 452 Varmint or American
2)Brno Model 3 or 4 (used only)
3)Savage Mark 2 (heavy barrel versions)
What about the Ruger 77/22? Are they reliable?
Word!Don't cheap out on your .22 rifle... Meanwhile your .22 will see the most rounds of all your guns together.
As for guns, I would suggest the Savage MKII as your starting point. A good
Savage Mark II = awesome
in my opinion