looking to by a used grasshopper and would like some input whether i should go for 600 series or 700 series. i want a 52" deck and have about 1.5 acres. also would like to know what is considered high hours. i have a chance to buy a 2000 720 with 2015 hrs or a 2004 618 with 598 hrs. the 720 has a grass catcher and i could get it for $3000. the 618 is in better condition but only comes with the metal grass hopper and tube for $3500. both have 52" decks and both have kohler. the 618 has almost new kohler command 19 h and the other is 20 h just rebuilt.