You could yes, but if you have the component set...why not just change it all.
Taking the dash of really isnt difficult, it just looks well...scary!
Just be brave, its simple and you will get much more benefit from the new tweeters.
Trust me those standard tweeters are nasty, they used to give me sore ears. Especially with any music that had drums in it!
I have audiobahn components in the front running from my amp and they sound so clear. I then have 13cm pioneer emotions in the back and a 12" alpine sub in the boot. Think it gives great sound, even at loud volume!