sq spl good solid

Alright so i got a mtx 1501 thunder its the 2004 model. and its 1000rms at 2 ohms so lookin for a dvc at 4ohms. its not stable a 1ohm and i am looking for a used sub goin for around 200-250. just lookin at what would perform the best. both spl and sq. not lookin at whats for sale just...