Upgrading Polk RM6750 speakers (w/ Onkyo Sr606)

[statikcat]

So I am looking into upgrade my speakers for obvious reasons. Here is my Polk set now:

http://www.amazon.com/Polk-Audio-Cha...5676380&sr=8-2

I am planning on getting Polk T15 for backs :

http://www.bestbuy.com/site/olspage....=1207956903491

I am planning on getting Polk CS10 for center:

http://www.newegg.com/Product/Produc...82E16882290105

Now what I am not sure is what to get for the fronts. It seems like current Polk speakers for fronts are all out of my price range. I am looking to spend 200$ or less on two front speakers.

So far I have my eye on Sony SSF5000:

http://www.bestbuy.com/site/olspage....=1172277278079

At 150$ a pair this is certainly in my price range. Aside from the black wood siding being kind of fugly they seem like a good value.

Will having half Sony/Polk setup cause any issues? Is there a better speaker set in this price range to get? Does anyone know any online stores that are still blowing out the Polk 50s? Would they be better? How much better will this level of speaker sound compared to the current Polk system I have?

Thanks for any guidance I have been searching this forum for a few days an gathering some info but am getting close to purchase time!