My thanks to all of you for your advice. I did finally get to audition the DefTech Pro 100's and Pro 80's at home and I must agree with member SHOE that I was underwhelmed with their performance in my 18'x20' room. In fact, I found my current mismatched setup to be far superior for music, and somewhat better for surround movies and dvd's. The one improvement I heard that was significant was in the center speaker in which the Pro 100 was far superior to my existing Polk. Once again, my current system is composed of Polk RM series 2 for surround, center and sub; and two old but wonderful full-size bookshelf speakers, ADS L 1's for right and left. My current feeling is to seriously upgrade my center speaker and continue with the current set-up. I do have an extra pair of small bookshelf Infinity "Sterling," and I will try out Shoe's suggestion as to satellite vs. bookshelves. Thanks Shoe. As before, all comments appreciated.