2 ohm or 4 ohm

That amp won't be stable at 1 ohm. And even if it was, it definitely wouldn't help the SQ. If anything, it'd hurt it.
If you're looking for more SQ, look at changing your box design. But no matter what you do, L7's just are not SQ subs. They're pure SPL subs.

Not to mention the fact that if you bridge it, the amp actually sees twice the load, so if you bridge it to a 1 ohm load, the amp is actually trying to run at 1/2 ohm per channel. Always keep this in mind when bridging an amp. If you are planning on running this amp bridged, you can NOT bridge it with either of those woofers. The DVC 4 ohm will present 1 ohm per channel, and the DVC 2 ohm will present 1/2 ohm per channel - neither of which are compatible... If you are looking to get maximum power, you will use the DVC 2 ohm, and wire one voice coil to each channel of the amp, if you are looking for "sound quality" then you will wire the DVC 4 ohm the same way. To please some of the others who will tell you "don't do it like that", wire the voice coils of EITHER of those woofers in series, and THEN bridge the amp. In that situation, the amp will "see" 4 ohms per channel with the DVC 4 ohm woofer, and 2 ohms per channel with the DVC 2 ohm woofer. If you are REALLY looking to maintain ANY KIND of SQ whatsoever, then use the 4 ohm version.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Yes it definitely contributed to it, same with a bad ground more than likely. A definite no go. Fix to look at a different sub that has some SQ to back it up, a sub like the Eclipse aluminum series.

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Top Secret, I can tell you but then my wife will kill me.