you can scrap the zalman cooler, it's not any better than hte OEM unit.
I'm not sure pairing an Athlon II with a 280x is a good idea... you'll be severely bottlenecked.
I'd move down to a 270x and that should match better and also get your budget where it needs to be
There's also no reason for 16gb of ram.
you'd never be able to use more than 8gb with that CPU, it'd become un-usably slow before being able to use over 8gb