I could never in good faith recommend moving away from the GSP 301 unless your current pair is broken. That's an excellent-sounding headset with a wonderful microphone.

Of the models you mentioned, the Quantum One and G1 are both better deals for those prices. They also both have a slightly more accurate sound signature than the GSP 301 does, but not so much that either would be a huge upgrade.

If you're desperate for a change, I'd suggest looking at standard audiophile headphones (as it seems music is a priority for you over gaming) in the same price range. Things like the K361, M40X, etc.

Or if you still want a microphone, the Sennheiser team that made the GSP 300 is now known as EPOS and they’ve produced several follow ups to their classic headset designs. The H3 is the new GSP 300 and it regularly goes on sale.