Bring on the criticism...

I've done this with speakers that didn't even match.
Monitors on top of large monitors.
I liked it.

That's funny, but really what's wrong with this setup? I'm serious?

Depends on what's important to you when you listen. Assuming the amp set-up can handle it, extra speakers can give you more volume and bass.

The drawbacks include a loss of precision in imaging and likely interference nodes between drivers, just to give you two thoughts.

Not everyone listens for the same things in audio. If you like it, go for it.

Thanks fellas, I appreciate the input. I haven't done any critical listening, just rock and house music. Guess that's why it seems to sound good to me.

I would love to get a switch going where I could compare the two speakers better. I know it exists...any help?

If you can afford to do that, why can't you biamp?

Agree with Mlsstl. It will work for a sound reinforcement system, but you could pay a lot less for a PA system that could do that. For the musical subtleties, imaging, soundstaging, timbre of instruments, I think what you're suggesting could be a problem. Of course, you could consider a four channel system (Peter McGrath's preferred way of listening), but that will require some more electronics.