You do NOT have to buy them in Pairs!!!
I've actually bought a SINGLE SM450 before.
In fact, I've done that TWICE!!
Okay, I initially used the SM450 as a Center. Worked great. Sounded great. But not EXPENSIVE enough for me.
So I ordered another single SM450, and used them as a pair of Surrounds.
You just go to an AUTHORIZED DefTech dealer and request for them to SPECIAL ORDER a Single SM450. Because it is a special order, you won't be able to Return them for refund.