HK's are great. I have a USP 45 --great shooting gun. Is there an indoor range near you? You can usually rent guns there. Most will have a USP of some calibre.
$600 + is a lot of money; you should definitely try before you buy. Whatever you do, don't listen to the "expert" opinions of people that hang out at guns stores and gun ranges. Especially the people that work there.
You test drive a car before you buy it, and you wouldn't purchase a car based on the recomendations of people at an auto parts store or a website, for that matter.
I will say any of the guns you mentioned would be decent. If you go to a range, and you happen to be more accurate with one gun than another, don't let that influence your decision to buy too much. Any of those guns are capable of better accuracy than you or I. Go with what you are most comfortable shooting position of mag release, slide stop, etc.
Good luck