much better off with the HTC over a MC. HTC runs off flash memory and will be faster....the MC may get improved eventually though. id use a HTC plus a USB hard drive, cheaper, quieter, better.
only advantage to a MC is if you need all the extra inputs...i only see a need for 1 serial, the 777, unless your integrating your alarm too, you can "split" the serial though....
but if you need more inputs, 2 HTC's is a better option. you get faster speed, ability to link/ control 2 systems easier, and 2 remotes, retail for 1200 vs 1500
like it was said, c4 is more then turning your lights on and off. link it do you dvd player, when you hit play, lights go off, pause they come up to 40% etc etc. smoke alarms go off?, lights come on, furnace shuts off, outside lights flash, etc etc. you get the picture + distributed audio, touchscreens keypads. Its really apparent on installing c4 that the bigger and more complicated your system is, the more awesome c4 is.