That would be the exact same thing as wiring each of the two amps to a single sub. Your output is still 600w per sub. You could also do this with a single JBL 1200.1 amp.
It sounds like this shop either hasn't got a clue about impedence/output/wiring or is trying to push another 1200.1 on ya to put some $$$ in their pockets at your expense.
