Hey,

If the guy does not know that you need to use the microphone at room correction, I do not think he has experience with Meridian. Contact Meridian directly so you can get help from someone who is authorized.

The 861 is a great processor, so do not give up.

You should have a 5 year warranty as long as it is upgraded to a v8 by someone who is authorized to and do it.
A microphone is very cheap, but a dealer should help you out anyway with room correction/set up.

861v8+ID41 for DTS, HD621, MD600, 40th Anniversary System 8000, 808v5 Anniversary+ID41, 7200.2HC, 3200 (sides), 5200 (rears), DSW, Oppo BDP-93-EU, Kuro PDP-LX6090, Revox A77, Luxman PD121, PSAudio Perfectwave Powerbase for CD and MD600
PsAudio Power cables, AC12 to P10 and AC5 (to all other components)