I have a pair of 2-way ADS Model 400 speakers (8" woofer, 1' dome tweeter) that I bought back in high school 23 years ago (!). I'm running them off my 20 year old NAD 7100 receiver (50w/ch, 200 w/ch 'peak power'). Having lived overseas for several years, I recently hooked up this system again and it still sounds good. I just ordered a Sony M500 150w 12" subwoofer for the lower end, which the ADS's could use some help on. I'm also using this as a makeshift home theater system (with my Sony NC-665P dvd/cd changer). My questions are: Do speakers ever 'wear out' or lose sound quality from aging? Although they still sound great to my ears, perhaps a new setup would sound considerably better, if I could compare them side-by-side. Is current speaker and receiver/amp technology much better than the stuff I have? I guess I would be looking at an integrated surround sound 5.1 package (satellites, sw and receiver). How much would I need to spend to get a setup that would sound *significantly* better than what I have? Also, is there a way to add a center speaker to my stereo receiver? Perhaps somehow bridging the Speaker B outputs so that the signal would be monoraul? Thanks in advance for any suggestions.