Do you own boots or have you just been hiring them so far?
If you don't have any, I'd really suggest that the first priority with that 600 is to get some decent, comfy boots! Your budget is plenty to get a nice pair, a decent deck, and still have some leftover for refreshments on the slope
Being a size 12, you might want to consider getting a boot with a reduced footprint size, such as the Burton Imperial or Salomon F20. I've heard good things about both these boots and it would open up your board choice a bit more as you may get away without having to go for a wide board.
The Capita Totally Fk'n Awesome may be a good option for you - it's what I ride and I'm a 80% mountain, 20% park kind of guy. It's not officially a 'wide' board, however it is made a bit wider than standard - I ride a 159 and the width is 25.9cm i think.