I have 1 dvc 2ohm subwoofer and 1 dvc 4ohm subwoofer. What is the best possible wiring? What amp? Both are 400 watt RMS?
Use one speaker or the other. Wire the voice coils parallel and pick an amp that is stable at or below the total impedance.
It's not usually recommended to operate subs of different brands or models together. They often sound muddy because they don't have the same sensitivity or frequency response. Unless you are talking about identical subs except for their impedance, I wouldn't bother myself. But if you're going to do it anyway, there are a couple different combinations. I'd put the voice coils of the 2 ohm DVC sub in series, making 4 ohms, and put the vc's in the 4 ohm sub in parallel for 2 ohms. Then wire the speakers together in parallel to each other and connect them to a 1 ohm amplifier. Their total impedance wired together will be 1.3 ohms. As long as the total speaker impedance is higher than the minimum stable impedance of the amplifier, you're ok impedance wise, but you also need a good power match too, so you'd need an amp capable of supplying 800 watts at 1 ohm. In this situation you could get away with an amp rated anywhere between 600 watts and 900 watts rms without worrying about it at all. An excellent choice for someone on a budget would be the Pioneer GM-D8601 that you can find online for around $125. It is rated 800w rms @ 1 ohm and is CEA-2006 compliant, meaning it actually puts out up to its advertised rated power. Brands that don't rate their amps according to the CEA-2006 standard often don't even make half their rated output.