Well, this may not be great, but depending on your leg problems, have you thought about a stand on mower?The only ones I have seen are all commercial level, so at homeowner level they are rarely seen. For a yard the size you speak of you won't be on it for very long of a stretch. And with your hilly spots you spoke about, it's much more stable and safe to use on them than a zero turn, especially a homeowner grade one. The decks are front mounted so you can mow under low bushes without loosing an eye or lacerating yourself. Your neighbors will have never seem one, and you would have your yard knocked out in record time. You will be DA MAYUN!!!!! Toro is probably the largest of manufactures for them, and one of thier machines is a 12 month a year machine with snow blower and power broom ect, but now you are getting pretty high in total ticket size. From what little I've seen (Full disclosure I only have a Honda HRX217VYA which my wife LUVES), But my choice for your yard would be a Bob Cat Quickcat4000 stand on. It's at the high end of your budget, but buy before the end of may and get $500 off, and it has a 6 year warranty, and depending on the deck size has either a hydrogear zt 3100 or 3400 transaxle. Anyway, just the thoughts of a lurker.