I have both a Homelite Ranger and a Redmax 400. You are doing right to use the Ranger for the stumps. The Redmax is too nice a limbing saw to ruin it flush cutting.
My Ranger I got used and it just needed new fuel lines, filter and a carb rebuild. Starts easy every time and runs well, just doesn't have a lot of power.
If you find yourself needing a bigger saw, take GrassGuerilla's advice on the Poulan 3400, 3700 or 3800. They can often be had in the $50-$100 range if not running, or the $100-$150 range running. The non-runners usually only need the fuel line/filter and carb rebuild treatment. They will run stronger and are tougher than the Stihl Farm Boss, for 1/2 the price. And if you know how to rebuild a carb, they are NOT hard to start. It is no coincidence there are lots of them around, still running strong, 30 years after they were built.
Also, semichisel chain works better than full chisel for dirty cutting - doesn't dull as quick..