I've had it for about two-three years now, and the bottom left speaker hasn't worked since.

All four speakers are matched "Fender Special Design" 12" speakers, with the blue sticker on the back.

I've been thinking recently to get a replacement, what should I look for?

Should I get another Fender speaker? I was kinda thinking of getting a Celestion, but what kind? How many watts should the speaker be? And I have no idea what ohm's mean.