I have the QS4s. The only issue with them is that you have to cross them fairly high--I think I have mine at 100 or 120 Hz. If your pre/pro or receiver doesn't have variable crossovers, that leaves you in an interesting place with regards to your mains and center.

BTW, I wouldn't put too much credence into the THX standards.

I am the Doctor, and THIS... is my SPOON!