Lude Generation

Hi.

I'm looking for new battery as my sound system killed the current one.
Not very often listen to the music when stationary. But when I am then need lots of power (DLS A6 + DLS A4). I was thinking about battery made for CA, but not sure which one. Would like to have it smaller than bigger as it will be relocated to the boot. Will SPP680 be enough? 230Amps, but only 20Ah

If I go with smaller then OEM battery should I replace my alternator for bigger one?

I use the Stinger SPV44. On my 2nd one now As the 1st one was bought 2nd hand but that lasted me 4 years of deep cycle use.

It's runs my 3 amps fine.

SPV44 is around £160 on egay. I had my battery for around 5yrs now and it have to be dumped only because it's sealed and I can't add deionised water. But it cost me around £80. So I can buy 2 of them instead of one stinger and there is a chance they will last for longer then stinger. Am I right? If so what am I missing and is it worth to pay extra for good looking label?
BTW there are some batteries for as low as £40 so I can have even 4 instead of 1 stinger but I do believe quality of them is...

I believe the Stinger I had was 3 years old before I got it. A stinger is a deep cycle battery so it will keep voltage until it drains the will recharge with no effects on the life. It can be drained over 300 times Where oem batterys can get damaged after a few drains.
Also mine weights 12kg where OEM is 18kg.

Other than that a £40 oem batteries will do everything else the same.