All depends on pattern of usage. You'll need to ask your ricer friends what they do. The group 49 battery is rated 8-900 CCAs. Bear in mind, it's the alternator that powers the car when running. It may not be strong enough at stoplights to power the amps.
If you run curbside for any length of time on the stock battery, you may be hurting.
Consider seeing an otologist.
Ed in San Jose '97 540i 6 speed aspensilber over aubergine leather. Build date 3/97. Golden Gate Chapter BMW CCA Nr 62319.