I want a cell phone that can i can listen to music from??

ok, im getting a new cell phone this month and i want one thats inexpensive and can play mp3s on it. however, i have ipod headphones and i heard that you need a phone with a 3.5mm headset jack just to use them, is that true, or if i buy a phone with a 2.5mm headset jack do i need to buy new headphone or what. tell me as much as you know about mp3 phones and headset jacks and stuff like that. also i want a phone that i can plug into my FM Transmitter in my car, i have Alltel as my phone company.