I see where you're coming from regarding the importance of flat-response headphones, especially when working with a modeler like the HX Stomp. Studio headphones are definitely ideal for critical listening and dialing in tones accurately. However, not everyone may be looking for a perfectly neutral sound, particularly if they're just jamming or experimenting with different setups.
Beats by Dre, while bass-heavy, can still be fun for casual playing or getting a feel for your patches. That said, they’re not the best choice for precision work, as their boosted low-end could mask the true sound of your patches. If you’re serious about using the HX Stomp for performance or recording, a better investment would indeed be flat-response headphones or studio monitors.
On a side note, if you’re considering switching to wireless headphones like AirPods for convenience, one issue to be aware of is connectivity. AirPods disconnecting during use is a common frustration for many users. For solutions, check out this helpful guide: AirPods disconnecting.
Ultimately, your headphone choice comes down to personal preference and use case, but investing in gear that helps you hear your tone accurately is always a smart move!