I currently have a 5 channel amp (600w on channel 5) pushing an Image Dynamics IDQ12. It sounds pretty good but I always knew my 5 channel amp would be upgraded one day. So, I am trying to figure out a strong amp/sub combo. I can build the box myself as long as it's sealed or a pretty straight forward ported box.

Local shop suggested Audio Dynamics AD4210 (~$400). Which is a 10" sub. Along with a SFB-1500D (~$270). Can anyone give any thoughts on how well this would perform compared to my current sub? It is a 10" but it's seemingly a higher end. And the power going to it would be double or more.

I am not dead set on the above combo but would like to keep the cost around the same (700-800) max.

Any suggestions?