I'm looking at a Scag Ultimate hydro walkbehind with the advantage deck. I've heard that the Scag walkbehinds are great it is just the ZTR's that suck. I'm looking at the 52" model and I can get a 17 or 21 horse Kawasaki. I will be mainly using this for really steep hills and small residentials. I wan't to run a Pro-slide as well. I've done some searching and everyone seems quite happy with the 17 horse, but there seem to be no comments on the 21 horse. I like as much horsepower as possible, but is 21 overkill? Is this what I should be looking at given the intended use?