My take on the OP's question:
For $500, your not going to get anything that sounds world class or whatever, so I'd say get a pair of PX100 and a transit. Spend the rest on music.
Every rig, no matter how lavish, can always use more music.
Option B: Forget you have the $500, put it away someplace safe, then save up another $500. Repeat the cycle 3 more times. Then re asses the situation.