I’d say the most value you can get from a omega speedmaster. The Lemania movement is one of the best and beautiful.
Zenith definitely also has a iconic movement can’t go wrong with that either.
Ap offshore is also a possibility if you want something bigger
Lastly a curveball. JLC Polaris perpetual calendar. I know it’s not a chrono but the dial is also complicated looking with a higher complication and beautiful finish.