There are two basic solutions for your situation.
The first solution is what's in your head. A sensor (that's where you point your remote at), connector block (where the signal is collected and repeated) and the blasters (that finally get the IR signal to the components). This is the solution that I use. I have a NILES system (
MSU480 ) with a big connector block, enough for 3 different sensors (inputs) and 8 single blasters. The wires from the sensor to the connector block can be very easily extended with CAT5 cable. In fact, that's what the manual tells you to do. As for the blasters, all but one of the blasters are directly connected to the connector block. The one for my projector is extended with a cable from Radio Shack, so that I didn't have splice that wire. I could've, but didn't want to. I spent about $430 ($280 for the connector block, $100 for the sensor, and $50 ($10 x 5) for the blasters.
The second solution is to get remote control system that has RF. There is still a connector block and blasters, but the sensors are replaced by RF. The RF remote will send a RF through walls to the RF connector block and that will transform the RF signal to an IR signal and use blasters to get the signal to your components.
There are two major advantages to using RF. The first and foremost the bestis that you don't have to hold the remote in a certain direction. The signal will always find it way. This is especially good for long macros, i.e. Turn on the projector, turn on the receiver, switch to DVD on the receiver, turn on the DVD, etc. The second is that it doesn't require any sensor, so you don't have to run wires, splice wires, or have a sensor near your screen.
Sorry for the long wind, but I was in your shoes a year ago and I wish I had someone explain this to me.