I've been reading a lot of these posts, and the possibilities seem endless (what i like

Right now, i'm totally renovating my house (just bought it, and i need to replace almost everything, elektricity, switches etc... )
But i like to integrate a domotica system as well, but i don't really know where to start.
I would like to start simpel, but i want to keep it flexible, so i can do whatever i want with it later.
I like to start with the lights, right now i bought normal single-pole (and a few double-pole) switches (but i'm not sure if this was a right decision with the option for domotica...) These were not expensive tough, so it's not that important. I've read that there are the powerline domotica switches which you can put behind the normal switches and you can switch your lights on/off with this.
Is this a good option, or dou you guys recommend something else? Like trow away those switches and buy others, just for domotica ( and if so, which ? )
Because i want to controll the lights on the switch normally as well.
I've already placed new electrical wires on the entire top floor in my house, and the ground floor is still good, so i would rather NOT cut in these walls anymore.
(Top floor i still need to put in extra power pluggs, so i still need to cut in the walls in the top floor, but ground floor is not going to get cut

I like to use the HomeSeer program, because i think that this has the most open posibillities, but if you guys know something better, what should i use then?
(Keeping in mind that i want to keep adding more functions)
So in short;
-How to start? do i need extra cables or not? Can i use those in wall switches that work with the normal ones,and normal cables ? And which are the best price/quality ?
-Start simpel, first light control, and offcourse it shouldn't cost to much, because i still need to renovate my ENTIRE house

-And what are other factors i still need to think of? I'm new to domotica, so i have really no idea ...
Thanks, and hoping for your toughts !
Dennis