First off, I do believe that Gonk is a Computer Server sitting somewhere next to an Outlaw execs desk, because no human being can hit so many places and be correct so many times and hold down a job in the real world.

With that tid bit of humor shared, it comes as no surprise that he is right. You always go with matching speakers when dealing with midrange and treble so that you match transients and have a seamless presentation without colorations from different driver types.

Identical L-C-R is ideal, but in the real world you really need to get a dedicated center specifically engineered by the same manufacturer to match your mains, same goes with surrounds.

With Bass it does not matter if you go with the same manufacturer or not, just find the tightest, lowest pant flapping sub within your budget.