The DA6213 would be a poor choice for your sub then. That amp is designed to put out it's max power at 4 ohms. With a dual 4 ohm sub, you have a choice of 2 ohms (parallel wiring) or 8 ohms (series wiring). You can't run that amp at 2 ohms bridged, and if you run it at 8 ohms bridged you will only get like 425 watts out of it. It's fine to run it at 8 ohms, but it is certainly not ideal.
So you have a couple of choices, switch to a dual 2 ohm sub and keep the amp....or keep the sub and find an amp that puts out around 1000 watts rms at two ohms.