I'm trying to decide on the sub for my G. I see with virtually all models of subwoofer they come in a 2ohm and 4ohm impedance, but I don't have a clue which one I need.

I'm likely going to get a single Kicker L7 10" solo baric with dual voice coils. Can anyone tell me which version I should get?

 

Which ohm you get depends on how many subs you are going to run, how you are going to wire your sub and amp.

For 1 sub connected to a standard 4 ohm amp you will what 4 ohm coils. If you get dual voice coils it will change the ohm load depending on how you wire it.

 

The big issue is if your amp is, say, 4 ohm minimum load . . . you can damage the amp if you have 1 speaker that is rated 2 ohm hooked to it. So in your case if you're buying one woofer only, make sure the amp's minimum ohms is equal to or less than the speaker.