The 561 is incredibly flexible as it has so many inputs. In terms of sound quality, they are very similar although a fully upgraded 565z3 may have a small sonic advantage.

I would definitely recommend looking for a used 568. Even a 568.1 will beat the 561 sonically as it has better processing capabilities. I moved from a 541 to a 561 and then onto a 568.2mm, and every time, there was a noticeable sonic improvement. It also depends what you are using with the processor (i.e. analogue or digital speakers) - the 568's analogue outputs are far better than the 561.

If you are looking to upgrade, don't rule out the G-series, they are still good processors!

Hope you manage to find one.

Cheers,

Steve

Main: 861v6 (LPS), 808v6, UHD722, DSP8000SE Anniversaries, DSP5200HC, DSP7200.2, SW1600, Sky Q, Cambridge Audio BD, Roon, M80
Office: 861v4 (LPS), 818v3, 800v4, HD621, M&K S150P, DSP5500HC, M&K MPS2810 sub x2
Son's system: 861v4, HD621, DSP6000.2, DSP5k.2C, DSP33, F80
Spare: MCD, 100 Series, 200 Series, 500 Series, C15s.