I need to replace the battery in my E46 M3. In my understanding, I escape the need for all the "registration" hooey required on newer cars. However, I haven't had to shop around for batteries in 15-20 years. BMW parts quoted me $179 less the CCA discount. Local auto places are quoting me roughly the same for an Interstate battery. Given roughly equal price, is one better than the other? Or maybe I should look into Diehard as well, having just thought of that as I type this.