I've been thinking of upgrading my center channel to something that can produce deeper bass, and perhaps mesh better with my fronts (old bookshelves that go down to 50 Hz). I've looked at center speakers, and have noticed that frequently, they are more expensive than a pair of bookshelf speakers, and most certainly more expensive than a single bookshelf (assuming that one can find a retailer selling single speakers). What are the advantages of the center speaker over a bookshelf? I don't have a large screen, and assuming that I purchase a magnetically shielded model, will a bookshelf produce acceptable results? I have a onkyo-502. I use it for a mix of activities: DVDs, HDTV, Music, radio (NPR), etc.