Do you think an organism with 1200 chromosomes would be more complex than one with 46 chromosomes?

Not necessarily as many plants have double or quadruple the amount of their DNA each time they reproduce (polyploidy). This phenomenon doesn't in fact change them.

This best seen when you think about some diseases seen in humans like Down syndrome where there is an extra chromosome 21, but this addition (aneuploidy) did not add to the complexity