Try a new alternator and check the fuel pump
Just kidding. The MBD isn't the greatest, and what KIND of PSU. It COULD still be the PSU, especially if its a cheap-o.... course I doubt it. Try a PSU from one of the other systems if you wanna make sure. Couldn't hurt. I dont think it would be underpowered, most everything you have on it shouldn't tax the system. Also, check and make sure that vid card is firmly seated. Some times you think its in but with a little more force it'll snap in a little farther.