I may be starting on this within the next week or 2. I have all of the parts you listed minus the parking brake override and head unit.
Check out the one that I am going to get. It is cheap and I think performs all of your desired function. Alpine ILX-W650.
I also have not purchased the backup camera yet either.
I have a customer who owns a very large and very successful car audio installation shop (that's just one of the things they do) and he recommended this same radio to me yesterday.
$250-300. I haven't looked in to it too much, but it may be the route I take.