There is no way a HPX200 or 500 is going to live up to a highend HD camera, nor should anyone expect it to. After all, look at the cost of HD lenses that are being put on Varicams, F900 and now the HPX3000, they cost more than what most people are paying for an entire HPX500 setup, no way is it going to be as good. But the question is what can you afford and well that do well enough for your needs. Get the best camera you can afford that meets your needs.
I have the HPX200, love it, clients love it, have used the 500 a couple of times and it offers some much needed improvements, what better with low light, bigger lenses but that comes at a much higher price, when I can afford a 500 I plan to buy one.