Guide me on upgrading from Astro A40 TR+Mixamp Pro to an entry level audiophile set up.

Once a reasonable next step up from my current set up.

PC gaming with an Astro A40 TR headset plugged into the Mixamp pro.

Should I start with buying a pair of sennheiser cans and plugging them into the Mixamp with a sennheiser boom mic for now?

The top of my budget is $300 what would you suggest? I’d prefer to have a minimalist set up for the mic, for example I only want to use a boom mic. I have a USB fifine mic but I rarely use it and have it in the closet.

Use case is 95% online gaming with friends. In a quiet room with no need for noise isolation.