Battery help?

Can someone comment/advise me on a battery that is long lasting and can more importantly take the abuse of a stereo system with subs that get's alot of play time while on the boat. (engine not running, just anchored out on boat.) I currently have 2 yellowtop optimas in tandem that are about 5 years old and they seem to not hold a charge as long as they use to?

thankyou in advance for any comments.

trojan t-105's.

I use Interstate 1 Deep cycle 1 starting. My Interstate dealer said the optima are made for rough service like off road racing and not worth the extra cost for a boat application.

I would second what Sam said. Deka also makes good deep cycle golf cart batteries. 2 6V golf cart batteries will get you way more play time then the optima's and will be way cheaper.