Sony MDR7506 $80 on Amazon, not sure if it would be an upgrade, but they are nice. My dad had a pair from a previous generation of the same headset in the early 90s when he was in the military. Lasted him about 2 decades until one side finally broke when i took one ear off so i could talk to someone. I got him either this pair or one similar to them, and he loves it, has had them for 3 years or so, probably gonna get a pair myself at some point, I need a good pair for music specifically. Very comfortable, great sound quality, probably not Sennheiser quality, but still really good.

Shure makes good headphones. Can get expensive. Had a amazing set when I was a dj

Sennheiser makes very good headphones and if you want to try something different you might want to try closed-back headphones made by Sennheiser or other audio company such as AKG, Audio-Technica, or Shure. The biggest advantage of closed-back headphones is noise isolation. To be honest with you, if you like your current setup stick with it, however if you want to try something different you should definitely consider upgrading you sound source. Look up Cowon Plenue D, they usually go for less than $200, you can find them on sale for less.