i have a mtx thunder 801d amp to power whatever i get. But i don't know what to get, i had one r but it wasn't loud enough.. so which of the two choices will sound better. Both choices would be put in a vented box
If u want sound quality go with the X but put it in a sealed box. spl/sql i would go with the Rs in a vented box. I have two X's in a vented box with the alpine specks and it hits very clean and hard. i probably should have sealed it but i like the spl too much. the X is a great sub but it all depends on what u want in your system.