not an expert, but have had to buy my pan for several years now....what do you mean exactly by your premiums paid up to $500? If that is in addition to whatever the standard employer provided amount is, and you are purchasing at the employee only rate then get the EPO plan as you pay nothing for any of them and that would provide the least expensive co-pays should you need something.
If you are paying the employee amount yourself, then you probably want the center or right choice given your age and health to save some money. Whether you choose the middle or right depends on how much you want to gamble on you staying healthy as the cheapest up front program has you going to full out of pocket pretty quickly before if provides any real coverage $$.
Of course that's my non-expert opinion after glancing at it at pone o'clock in the morning