I'm leaning towards the 300 XCWe.
Pretty sure I'll be getting a new bike, and like riding the mountian trails more an more, so the light weight of the 300 is looking pretty nice. If not maybe the 450 EXC.
It also depends on what the 520 sells for, $8000 is a lot for a bike, and you can pick up 07 300's slightly used for $5500, maybe even new 07's for cheap.