The choice of which miicrophone(s) to use will depend on what you want to achieve.
you have indicated that you want a "living room all rounder".
Much will depend on how big your room is, the acoustics of the room (carpet v wood v tiles on the floor, type of walls, height of the ceiling, how many windows etc. as well as what other noise making devices are in the room ie air conditioner outlets, stereo, tv etc.
Is the room acoustically "flat" or "bright".
How much is your budget.
that said you can do alot using ebay and getting 2nd hand audio conference equipment and microphones.
If you want an open air microphone system - it can be done but you will need to get the right equipment and spend time adjusting and tuning it.
After many hours over the past few years - I am finally getting my open air system to work consistently at around 95% accuracy.
Having VC has really helped.
My current setup consists of the following:
3 ceiling mounted beyerdynamic MPC22 microphones in 2 rooms. (ebay cost from $20 - 150 each)
They are connected into a Polycom Vortex conference mixer that supplies phantom power to the microphones.
For each microphone input -the mixer can provide Noise cancelling, Auto Gain Control (AGC) of up to 10dB along with both low & high pass filters.
It also has auto mic gating.
The output from the mixer is set to a line level of 0db into a Behringer UCA202 which is plugged into my PC.
I also use ceiling mounted speakers in the rooms to direct the music & Voice replies from VC downwards - away from the mics.
I can now be anywhere in my kitchen or lounge room and talk to VC and it will hear me and respond.
I am planing to expand the system into other rooms in my house in the coming year.
here are some web sites that may also help you
http://www.iautomate.com/pages/Whole-House-Microphones.htmlhttp://james.lipsit.com/whole.htmhttp://board.homeseer.com/showthread.php?t=104567