You can def be to big..... If you have a huge stove it will idle many times longer them what it should and could lead to creosoting problems as well possibility of the fire going out. It will also make itself very inefficient, because to keep enough wood in it to keep it from going out, it'd just to much wood and that again leads to creosote.
I always tell customers don't cram your stove full, it's wasteful and silly. Just add enough to get you through to your next load time. But I still have folks cram them full no matter the weather or conditions
What is considerd a good deal on that unit, kinda curious