the surrounds are very important, in my opinion. the surrounds are what creates the 'enveloping' sound that makes HT sound so good.. both the QS4's and 8's are terrific speakers.. depending on your room size and budget, the 4's might be a better fit for you..
with that being said.. if you only have a certain amiunt of money to spend at a time.. and with you having a spare set of polks that are just gonna be laying around.. it would make sense for you to go ahead and get a center, and use the polks til you can get something better.
there is/will be a difference in sound when you go with the QS4's or 8's, but there are other factors to keep in mind.. budget, availibility, etc.. make due with what ya got, and look to upgarde later.. and if you dont have a sub for those M22's, get that before you get a center!!
bigjohn
