HD650 over the 880. It's a different level, DT880 is dry, lean, bright, higher distortion weird depth to it's soundstage.
650 is warmer, better detail and resolution, smoother through the whole response. It's just better in all areas.
I really enjoy the DT770 it has high distortion and issues but for a closed headphone I think it punches above it's weight but the 880 doesn't in my honest opinion.
The 770 has a warmness to it and due to it's closed, thunderous resonating closed cups it did hide a lot of problems all beyers have which is lack treble smoothness. The open Beyers are a different monster and not always for the better if you like a smoother, more natural response. The who open line is lean and bright.
The 650 is just that damn good and the next full upgrade is probably the Audeze LCD-2 + 3) but even then the 650 beats them in areas and due to the lack of consistency, very often beats them. Hifiman HEX(£1300) but even then early impressions are saying the HD650 is better in key areas so maybe something like the HE-1000(£2800-£3000)
A side grade could be the Nighthawk(£500) which wins in treble extension and detail, distortion figures and bass extension but loses in mids, cohesiveness and micro detail(just about)