To indicate how simple you could go, on my HTPC machine I'm using my TV remote. It's a Panasonic, 8-in-1. I can turn the HTPC on with the same signal as turning on the TV. The DVD functions are mapped to control Zoom Player and the AUX setting is used to control Xlobby using the Mirage skin. There's also VCR, DTV, DBS, Cable, and RCVR settings which I have not mapped...yet
. This is using XRemote/Girder/WinLirc. The powering of the system is a MayIR
On my other system I'm using the Hauppauge 45-button remote for everything except for turning the system on. I had to modify the Hauppague's irremote.ini file for zoomplayer control, but works really smooth, even navigated throughout xlobby without any intervention. I have a Hauppauge PVR-150 in that system, which included an IR Blaster/Reciever. No additional software or hardware required. I'm going to add a MayIR to that system so it can be powered at the same time as the TV though.
My third system using Xlobby is the music-server...no remote here, purely being controlled by a PPC.
Again, this is showing just how simple you can go.