Just talked to Chris at Aircraft Exhaust Technologies. He said the crossover system for a 7A with mufflers is $1149, which includes the heat muffs, tail pipes, gaskets, etc. The post on the VAF page makes it sound like you can swap out parts from the standard cross-over pipes, but Chris said you can't just put the mufflers on Van's standard pipes. You have to buy his complete system because of slight differences in the upper sections.
Van's cross-over pipes are $795 as a point of reference. $350 extra isn't bad for mufflers and increased cabin heat.