Blue Skies thinking for IWBs
2 Thunderbolt connections in the wall.
Laptop/PC into one, optional Visualiser into the other.
Thunderbolt connection to the 'interactive projector' which contains built in graphics, audio and LAN card, mini amp and (optionally external) speakers.
Cost of the extras off-set by the massive reduction in install times: No board, no complicated wiring, just two premade cables, a connection plate, a projector (and optionally two speakers)
I'll likely be looking for a IWB installation again in 3-5 years. See above for my specification. Get to it. :)