The stock tweeters are 2" They use a crossover that is lower than most of the aftermarket ones, that is why good stock tweeters sound better than a lot of aftermarket ones.
I replaced mine with these:
http://www.alltronics.com/speakers.htm Scroll down to the Mini Horn Tweeter #99V003.
They work awesome in the SVX. I use them in conjunction with Polk 6.5 door speakers and Polk 6X9 rears. The second SVX originally had the Polk 1" in the dash, but they sounded so bad, I changed them.
Doug