Could you not bash a hole in the wall and sit the DSP5000 in the hole
Make a wooden box for the hole, then buy a grill to cover the box & hole, there are companies who'll make the grill to the size of the hole very similar looking to Merdians in wall grills.
You could pick up some DSP5200.2s for near the same price as the Meridian 520 in wall centre, money better spent, i have some 5200.2s they're pretty good even on their own not through a processor, a bargain at today's prices.
They kind of sonically match an old M60c, the predecessor to the DSP5000c (or matches enough for the £100 the M60 cost)
2k+ is a lot of money for centre speaker, sure some can afford it, but seems a bit much regardless.
If i ever go inwall, i'll also bash some holes in the wall or add a false wall, then sit regular Meridian speakers in the wall and have grills commissioned.
Loads of money saved.