I built my own PVC cage and have been very pleased with it. Even though it's 24" high and my living room gets down to 55 degrees, I have no trouble heating it. I use a 80 watt rhp mounted under a platform instead of on the ceiling, which let's the heat make it all the way to the floor, results in less loss out the top, and turns the platform into a nice basking area. There's insulation between the platform and the panel so the platform surface never gets dangerously hot. The platform is large enough to have substrate and hides on it, and it gets used quite a lot. I also have quilted panels covering the whole viv except the front, and I use acrylic doors instead of glass because they retain heat a bit better.
If you're only keeping one snake, you might as well give it a nice big enriched viv. Heating doesn't have to be an impediment.