technically yes, you can. but be careful with room size. i have a 14'x18' room and they are MORE than enough as front l/r. i can't imagine how it would sound with them set for rears as well.
depending on room size, if you are dead set on getting towers for the back you may want to look at the 9040's or maybe the DT offset surrounds.
but yes.....they would probably be awesome for surrounds.