You mentioned some HO cars, but you also said you have a 3 lane track, which might confuse some people. For regular modern inline HO cars that are run at 18-20 volts a 45 ohm controller would be the thing to start out with. The latest AFX Mega G+ cars need a 120 ohm controller, you probably could get by with a 90 ohm controller in a pinch. For pancake type cars like the original Aurora Thunderjet and the newer Johnny Lightning and Auto World clones of those most people use a 90 ohm controller. When it comes to cars and controllers one size does not fit all, so you might be better off asking about controllers for specific cars.
With respect to all the different types of HO cars here is a good reference:
http://www.modelmotorist.com/web-content/idchass.jspYou will have to click on each make and then look at the pictures.
If you have a power supply with an amp control always leave that turned all the way up.