Hi Tom, and welcome to the Gauge.
I have two of the Spectrum Ten-Wheelers, but haven't run them very much, as I can't make up my mind as to what roadname I should modify them to. They're both very smooth runners, but don't pull an awful lot, due to their small size and comparitively light weight. Like all Spectrum steamers, current pick-up is both through the loco and the tender, so they seem to be trouble-free through turnouts and over less than perfect track. There's not much room to add weight, either, as the boiler and cab are both metal castings. If you don't have any grades, and if your curves aren't too tight, one of these locos should be able to handle...wow! I hadn't run these locos too much, so I just went and got one of them out of the box for a test run. Using free-rolling cars, mostly on Proto2000 trucks, the little loco that tried actually moved seven cars around the layout, without too much trouble. Most of the curves are 34" radius or larger, but two of them are on a 2.5% grade: there was some wheelslip going upgrade, but not excessive. On level track, one of these locos should be able to handle even more cars. Most of my rolling stock is not quite so free-rolling though, so my plan is to doublehead them on fairly short trains. Most of my passing sidings will only hold a 12 car train, so short trains are the rule anyways.
Wayne