Last night I went out for a "spirited" drive after the streets dried up (rained all day) and I noticed at one point that when the car was at around 5K rpm, my battery light was kinda trying to light up very dimly. The higher the rpms the brighter it would get, but it would turn off once it went below like 4K. I was guessing that the battery is probably about to die. Is that most like the culprite? (BTW no other lights on the dash lighting up, just the battery.)

Also, I was looking into getting an optima red top battery... worth it? aproximately how much can I expect one to go for at a regulay shop?

Is there any other battery I should look into, and for how much?