If you want to try a large format tweeter that is made for the GB60 than the GB15 is it. The GB15 is an incredible tweeter that can cross very low. If you can get the GB15 closer to being on axis than it would be even better. Mine are located in the factory locations in the dash corners and they are about as good as it gets for a two way like this. A good alternative on a budget would be the SB Acoustics SBRDCN29 neo magnet tweeter. I have these in my minivan and really like those too. It’s my opinion that you will not beat those SB Acoustics tweeters for that price range. I have my GB15 crossed at 2k Hz and my SB 2.5k Hz, both in active two ways.