The 500 is $150 on Amazon at the moment, but is still massive overkill for your situation.
The negs on the 230 are mostly related to features you'll never use, so what does it matter?
The Pio is excellent, but is at the top of your budget, and overkill too, IMO. Most of my players are $40 Sony 1100's because I only buy the functionality I need. You can certainly spend whatever you like, but it just seems a waste to buy more than you need.
Having said that, if you don't need optical, the 5100 is by far the best bang for your buck.
The majority of what I'd play on the BD player would be BD titles in both 2D and 3D, though there are some DVD titles that would get played on this player, so DVD upscaling performance is a secondary need though one that would be helpful. The remote on the Panasonic 230 seems like a trainwreck with the touchpad.