I just learned an important lesson in home exercise equipment yesterday, without spending a dime. My roommate bought a weight bench, and while cool, it doesn't have near enough weight. The bar weighs about 10 lbs, and the set has 155lbs of weight (or so) total.
This isn't near enough weight, not because I'm strong, but because it prevents you from having an effective workout. If I were to do bench press and curls with the dumbbell bars, I'll need to keep moving weight between the dumbbell bars and the bench press bars.
Knowing this, should I ever happen to buy any kind of weight-lifting machinery/equipment, changing between workouts will have to happen quickly, which will require much more weight. (BTW, I hate weight machines.)