For $500 I’d consider leaving the Quadro till last on your list.
The K2000 is basically (and without googling it’s hard to tell, but I’m willing to bet it’s actually the identical hardware based on specs) the same exact card as the GTX 650 just with the Quadro drivers.
You will get benefit in the drivers but that will come more in features/quality, not heavily in performance.
Consider for the same amount of money you could get a GTX 770 which has a ton more CUDA cores and much faster memory bus. There are pros and cons to each side, but I’d consider reading up more before dumping $500 into a GPU.