I don't know what your budget is, but I think you would be making a mistake with X10. If you decide later on to rip everything out and use something else it will be more expensive than making the best decision you can make now.

You should look into Radio RA 2 (cheaper than Radio RA) as your lighting control system. Setting up a computer to do a home automation or control systems job will get ugly. I'm not a big fan of it because I dont think it's here yet. Yes, you could do HAI and control your home, but I thiink you should invest in a control system to tie in here.