Ive had the XB500s for years. From what Ive read on Head-Fi and other places, these can’t hold a candle to the 500s, in sound quality OR bass (which is what these are made from). Send high-quality lossless amplified signal to the XB500s and they can literally (and I’m using “literally” by its actual meaning) rattle your jaw and blur your vision from the bass, and do it without completely washing out the rest of the music.
I’m sure these are great, but if you are shopping for someone who is intent on getting HEAVY bass, find a set of XB500s if you can.