Just finished my audio upgrade, I replaced front tweeters with JL Audio. Day and night. Now I have crisp and clear highs. My sweet spot was hit with the 2.2micro farad capacitor as a high pass filter. You will need a dremmel to remove volvo tweeters from their housing and then glue new tweeters into the housing. It was quite a project but the end result sounds like a dream. It was worth it. IMHO the rest of the premium system (no cente) sounds decent with stock drivers and there is no evident increase in perceived loudness of the system.
OEM Tweeter mounted (BEFORE)
JL Audio tweeter mounted (AFTER)