i have a ram mega cab and a sundown 2000d amp. what is the best 12in sub.

To vague of a question. Goals/budget?

Nowhere near enough information given for anyone to provide you with an answer. I'm not trying to be a dick, but read the terms and conditions you agreed to before posting a topic. You can find them here SSA Membership Terms and Conditions. You get what you put into a thread and with a thread like this you won't get anything. It's important to make a good thread so that others might have the chance to learn from it as well. With the right info myself and many other members would be happy to help you

srry my budget is gonna be less than 600 and i really only have enough space for 1 sub without doin alot of modifying. i want it to be pretty loud too

fi btl lol my bias opinion but plenty of other choice's

srry my budget is gonna be less than 600 and i really only have enough space for 1 sub without doin alot of modifying. i want it to be pretty loud too

have someone build you a good box for a nightshade 12 and put that 2000d on it, you will be very happy

i would usually say SSA Zcon... but Sundown subs like small boxes, so Nightshade gets my vote here.

orion hcca 12.2 has my vote!!!!

A bag of potatoes should put out about 199 dBz.

https://ssl.perfora.net/www.ficaraudio.com/sess/utn;jsessionid=154e1e6708d3091/shopdata/0050_Speakers/0010_BTL/0060_N2/product_overview.shopscript

That's 1 vote for a Fi BTL from me! just click the link.