So many good choices out there, it's ridiculous these days. Still, I'm a Marauder fan on the low end. It's a touch over your $400 budget, but if you can stretch for $500, it'll give you much more gun with much more future.
It's completely adjustable, after market parts are plentiful, and most of all, the knowledge on the forums is deep. If you have a problem, someone here can help, and the members are always happy to help.
My own Marauder in .22 was very accurate out of the box, and after some tweaking, after market parts like a regulator and such, it's even better.
The one thing most people overlook is the trigger. While this isn't an Impact Trigger, it is a good solid, adjustable trigger that holds up well. The Fortitude and other inexpensive triggers tend to be heavy, mushy, and generally poor quality that impacts your accuracy. The Marauder trigger is a good hunting trigger that breaks cleanly and gives you what you need.
Good luck!