Upgrading door speakers with tweeters?

Hi, I’ve got a ‘96 polo and am running an Edge EDB12 sub with built in amp, 2 standard dash speakers and 2 standard door speakers off of my Sony head unit, will I need to run another amp to upgrade the door speakers and add two tweeters? Am planning on buying the Edge EDST216C with the accompanying tweeters! And also, can I solder the wiring for the tweeters to the metal connection on the new speakers? Thanks for any advice in advance! Rhys