I have someone who is interested in buying my 12" Type R in the box for $350.
If I decide to sell it, what would be a better sub that eats 500w RMS @ 2ohms that preferably hits harder than my current Type R. I'll be building a box to spec for whatever sub I choose, but what sub should I get?

Don't have enough money to go with a bigger amp.

 

DD2512 and the proper slot port box for it should do the trick. It will handle far more than the 500 you have now so it will leave you some room in the future for a larger amp should you like to upgrade.

 

How much of a difference would it be between the DD2512 and my Type R (both built in custom box's tuned to 32hz)?

 

Between DD and Alpine, should be night a day. The sub mentioned above (2512) will take 750 W rms and DD's handle extra power well. It should play awesome. It should be as loud or louder (my bet is louder) than the alpine any day.

 

off 500rms. hard to say what would be louder. type r's like to get loud.
dd loves it but with more power. pretty close call in the spl dept off that much watts.

 

Look into the Mach 5 audio MAW 15, I listened to one the other day off 600rms and it was awesome! Quite possibly the best bang for the buck out there when buying brand new. May not be "better" than the Type R, but it should be louder.

 

An IDMAX would do very well with 500 watts.