I own a 13 year old HRB that I love EXCEPT that the highest cut is only 3" and in the summer my lawn needs to be higher to prevent burn. Is it worth the money to upgrade to an HRX and how do the new engines compare to my HRB? The difference in cut height is only 1/2" but I think that might be what I need. I have no idea what I would do with the old mower if I replaced it. Can't imagine someone wanting to buy a 13 year old machine...