XBox 360, the current model, is not noisy at all.
Plus, it is really your only choice. Suck it up and go that route. Also suck it up and make sure you run wired gigabit ethernet. Period. Do not pass Go, do not come here and whine about how "that's too hard, besides wireless should work just fine". It doesn't. You need to hard wire. Suck it up. Beyond the 2GB of RAM needed to boot the PC and run WMC, each extender requires 1GB of RAM available to it on the WMC PC. So, for two extenders you need 4GB installed; for 5 extenders, you'll install 8GB. Period. Do not pass Go, do not come here and whine about how it shouldn't be that way. It is. Suck it up.
And yes, each TV behaves independently. The WMC box has a single guide and a single recording tank where everything is recorded to, and it manages all the tuners you have installed. It can send recorded TV to any extender, and it dynamically assigns a tuner to an extender if that extender user decides it wants to watch live TV.
You can control your WMC and recording schedule from any TV; you're actually controlling the WMC itself.
You may have more than 5 extenders configured, but you may have no more than 5 simultaneously active at any given time. That's how it is. Period. Suck it up.
If for some God forsaken reason you're watching live TV and the recording schedule wants the tuner you're using, it will pop up and ask.
In summary: go get an XBox 360 4GB and configure it to boot into WMC automatically, install it, and watch it happen just like you want. Then got get 4 more to round out your stable.