I would not call that a big enough upgrade, unless as mentioned, the price was really good. Changing out a tweeter is not super difficult, but it indicates the speakers were pushed too hard (insufficient power, not too much, common cause of fried tweeters) and that does obviously leave concerns of how they were treated. I'd check on the replacement tweeters first too as mentioned, because if they're pricey or unavailable, then it may not be worth the trouble.