The front three speakers should match.
Why not just bite the bullet and get two pair of the 652's and use one for the center. If your receiver can handle it, you could use the spare for the 6th channel*.
Actually, why not go for a full setup (three pair) of these. With a sub you can do amazingly wellfor that price, and you'll have a spare in case a speaker blows. Or, perhaps you could connect two 652's in sries for use as a center speaker.
*[edit] it won't. it's a 5.1 unit.