The 1641 is a mid '90's model. I'm pretty sure the basic layout is the same as my 1864. I looked at a spec sheet and it has a Vanguard 16 HP rather than the Kohler Command 18 HP that is in mine. Not sure if that is good or bad, I don't know anything about the Vanguard engine.
I'm very happy with my 1864. Fairly large machine but very easy to run and has a tight turning radius that makes mowing easy. I think you would be very happy with the 1641, just maybe get some input here on the engine, I know you will like the rest of the machine. What deck does it come with?