Dear Paul :) thank you very much for your detailed response)) The problem started like this: first my subwoofer was rattling as the cone moved up and down, i listen it 2-3 days like that, then subwoofer stopped to work. LEXUS IS(2nd gen.) ML SUBWOOFER is famous for failure as i read many texts about this in forums. I got it fixed it, put it back, after 20 min again stopped to work. Also around of cone was ripped. I thought its meaningless to repair it again. I put it there aftermarket sub ( we cut the steel to fit subwoofers lower side ). This sub is also was rattling sometimes(especially in bass songs) After 4-5 months front center dash speaker started to make noise(rustle), i replaced it with Lexus speaker (not ML audio system). Again after 6 months rear speaker(which is near to sub) start to make noise like dash speaker. So, in conclusion i think my speakers lifetime is finishing and i want to solve this problem fully. I don't know how to do; to repair Lexus speakers or to change all of them with other good aftermarket speakers.
When i bought car(second hand) there was a problem in ML amplifier. We fixed it. i don't think amplifier has problem now. But maybe as you say the problem is amp or crossover network(except sub). I will check it.
By the way i am not living in USA :) thats why i have to order speakers from internet. I need to know the size of speakers, ohm and etc..)