The earlier Z1000's were a bored-out ZX9R motor if I recall correctly.
I can't speak for the previous gen, but I had a 2010 Kawasaki Z1000 (That had the new 1043cc engine, a variant of the new ZX10R) and it was so comfortable, a very hot looking, great sounding bike, and the power band was smooth like butter. I'd go asking on the KawiForums, though, it seems the Z1000 is not a very popular bike. I think a few people on there are active that have them still. I will say though, it will definitely be a lot more comfortable commuting on the Z1K rather than the R6.