I currently have them in my A-Pillars aimed on axis, not too much worried about the passenger seat. To me their performance is better on-axis but could be too much in your face depending on volume or listening habits, so off-axis can be a plus depending on user. They are crossed at 2000hz at 24db, I could cross them lower but dont want to since I do like to turn my stereo up. Im using a PPI900.4 at 4 ohms to power them and an 80PRS for tuning. I havent played with TA yet too much.
But so far Im in love with them, they can play any genre of music without much change needed in eq (I listen to mostly R&B, Old School, Rap and some Pop/Country). Im not the best SQ person to listen to but in my opinion they give you the best of both words, output and sound quality. Compared to some other non-pa tweeters I have used. No matter the power level they put out great sound and they are really efficient. I ran them off head unit power with a cheap soundstream tweeter crossover and they still performed well (before I got my 80PRS). Im not trying to hype these SB Acoustics tweeters up but to me I cant find one downside besides size. But with my new mounting cups, its not an issue anymore really. Im not the best reviewer but I would recommend these tweeters to anybody. I spent months on months reading reviews on the interwebs about them and pulled the trigger over 3 years ago on my first set. I even bought a second brand new set recently to use in my new ride. I soldered 14awg stinger wire to my current ones and the wire wont fit in the all-thread. So I have a used pair that I need to find a house project to use them in (unless your interested in trying them out and want to save vs buying new). Hope that helps.
Aaron if you would like to add this to the product review section instead, fine with me as well. Just a short simple review, nothing too informative.