I have not ridden the K2 raygun but I have heard good things about K2 from a number of riders here in Japan.
I was looking at the K2 turbo dream as an all mountain board for myself.
I recommended it because is it would fit your budget and I hear K2 make very solid decks.
On further consideration the raygun may be a bit stiff if you mainly want to hit the park.
would be a great do everything board to start from and you can definitely do well in the park with it. You surely could find last years board (the same as this years apart from graphics) for less than 300. Maybe less than 250!
I own a ride highlife and demoed a number of their boards but not the crush because I rarely hit the park.
I prefer more all mountain and powder freeride. Still I have been on boards like the antic and manic which are more or less just stiffer versions of the crush. Same kind of profile with a flat base and rocker in the tips.
I love my highlife and I enjoyed the other boards I demoed. I like their boards a lot and they are well respected by shredders here on this forum.
They make a good solid board and if you mainly want to hit the park the crush would be in your price range and a very good board IMO.
A quick search reveled a 152 (the size you want IMO that goes for any board) for 230 bucks!
I am tempted to get one and start working on my park skills. Sadly because I live in Japan the postage would be just silly. Anyway here is the link I found. They also had ride EX bindings from last year for like 100 or so.
Ride Crush Snowboard
I found this in like a 2 min search. You could maybe find even better deals if you look.
The boards wiredsport recommended are also great boards. Either way you can be ripping a brand new board with a 1 year warranty for way less than 300. Hell you could maybe even be on a new board with new bindings for not much more than 300.