If the tweeter is 8 ohms, a 1.5uF cap will give 13250hz, 4 ohms will give 26500hz. Might be worth changing the wiring, I think any new cap you buy will sound a little different, won't really be a big improvement IMO. The existing cap will be fine.
“Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”
Hunter S Thompson