Honestly it sounds awesome. I haven't heard every speaker out there but these are the best ones i have had the pleasure of listening to. It was one of those things where i picked the speaker first and than had to figure out how to fit them.
When I was running aftermarket tweeters in the stock locations i was running into issues with sound wave reflections off the hump in the dash where the instrument cluster is. Having bigger speakers aimed up a bit helps avoid some of the issues my processor was having trying to time align the speakers (JBL MS-8).
Are you doing just tweeters or thinking about putting midrange speakers or widebanders up there as well? The biggest issue I had was with the huge magnet on the back of my speakers. If I did it over again I might have just gone with large format tweeters or a dome midrange and tweeter set up. What speakers are you considering so far? Maybe I can help you with some suggestions or thoughts on the speakers you have been looking at.