Thanks for the help.

Using the miniDSP and choosing speakers with optical inputs rules out the M6 but could use Meridian 5000, 5500, 5200 or 5200.2 with just a remote from my computer similar to what I am now doing with analogue active speakers.

D600 (1989) analogue and optical coax input, M60 (1988) analogue with the smiley face 3rd version in 2001.

Prices as recently on eBay.

DSP5000.1 1994 (£400, £800)
DSP5500 1996 (£1380-2000)
DSP5000.2 2001
DSP5500.2 2001 (£1800)
DSP5200 2004 (£1200, £2000, £5000)
DSP5200.2 2015

DSP5000C
DSP5500HC
DSP5200HC (£1100)

DSW
D1500
D2500

What if any the 16 plus year old speakers can still be repaired by Meridian, perhaps 5200?
Meridian, in an interview, suggest 12 year old speakers can be upgraded.

Meridian 101B/104/M1 MkII/D600(x4)/M60C & MCA,Linn Sondek/Ekos/Trokia,Uher CR160,Bose Videomate speakers,Sony RDR-HXD970/PC100/HDR HC7/EV-S9000E/VCC5000/WM-D6C/Nex 7,PC DVD-RW /Blueray-RW/Terratec DMX6FireUSB /Blackgold HD Freeview/ HD Freesat, Devialet Phantom Gold (x2)+Hub, B&W PV1