I went from Marantz to Musical Fidelity m6si and have been happy. Gave me more power and a familiar but better sound. I took my speakers to a few whops and listened to several to make sure they matched up. If new speakers are on the horizon, agree with others to match them.
Also, I use my old Marantz, repaired, to drive outdoor speakers. Might work for headphones too depending on your situation.