Not at all, I don't think you need a bigger battery in the current (excuse pun) position.
I would fit a second battery in the boot and a split charge relay. You then power all your sound from the second battery and the relay keeps them seperate so that you can still start the engine if the battery in the boot goes flat.
The Centos are analogue so all you need is a 30 amp switching relay.
I don't have the space in the boot for a battery unfortunatly, There's a sub and amp, then enough room for my bouldering boots, chalk bag, carpet square and water dip meter.