You could get TMCC level control or PS/3 by having an upgrade done but I think the money would be better spent buying a lower end Berk that already had command control. Otherwise, you are looking at $1500 or more for a SCALE Legacy Pere Marquette 1225 plus about $150 per car for the scale versions.
I have been running my P.E. set for a long time and though it isn't as nice as the scale, it is what it is. If your son likes the Polar Express, the set will grow on him.