A good audio interface is not overkill. It literally becomes the heart of your system. Also as Mario said a decent set of monitors helps when it comes to mixing. They need not be super expensive as the purpose isn’t to sound incredible, but to give a flat uncolored response so the you don’t over or under bass out a song. They are also commonly called reference monitors. Because help you reference what is a sound that will play well on many different types of systems. Car stereo, headphone, home audio etc.

Like the pic I posted for my system it is not impressive, but very effective. A good interface, decent monitors, a solid laptop, a small midi controller, and a suite of awesome software.

HP Win 11 12 gig ram, Mac mini Sonoma with 16 gig of ram, BiaB 2025, Realband, Reaper 7, Harrison Mixbus 9 32c , Melodyne 5 editor, Presonus Audiobox 1818VSL, Presonus control app.