Not sure if the original drivers in your system were matched, but a lot of manufacturers match the drivers that go into a pair of speakers. If you do replace, it would be worth the extra money to buy from a place that can match them for you.
Replacing speaker drivers...Improvements?
My speakers use Scan Speak 21w/8554 Mid/woofers. I have read where certain speaker drivers acutally sound better with age (esp, ones with Kevlar cones). There is nothing wrong with my current drivers, but wonder if anyone has experience with replacing drivers and seeing improvements over the older ones. The drivers in there now are approx 6 years old.