My dad gave me a pair of old Infinity RS1000's. I want to put new speakers in them since the original cones have completely rotted out (the foam surrounds are gone). The tweeters look OK, so I am just going to replace the one rotted speaker on each. How do I find out what the crossover is set at so I can buy the correct speaker? Do I just guess and get a "Midbass" or something? There is nothing on the back of the bad speaker (I checked). What size speaker will fit? The opening in the front is 4.125" (4 1/8"). I don't want to do any cutting. BTW, these will be my garage stereo speakers, so I don't expect miracles... I appreciate all of your help!