JL 12w3v2-D4 which amp?

The MRD-M301 should be plenty for that sub. You won't gain that much by going to the MRD-M501.

If your sub is actually 2 ohm DVC then you can't use a mono amp thats stable down to only 2 ohms (like the MRD-M301, MRD-M501, and MRD-M1001). You can either wire it for 1 or 4 like you said. If it is actually a 2 ohm DVC sub then look for a 300 to 350 watt continuous 2 channel amp.

Foolish:  honeslty dont waste the money on the 501 you WILL BE VERY HAPPY with the MRD-M301 as i said myself i have the D2 version i ran it off a 220*1 RMS at 4ohms on a alpine mrv-t320 for a month and the bass was pretty damn nice and tight. THen i got a amp that does 340WRMS *1 at 4ohms. and wow the sub pounds i dont htink any more power than this is needed. Is the box you are goign to be using a PORTED Or sealed im using a Ported tuend to bout 32hz and its very nice. in the summer months im building anew ported box with al ower turing frequency.

Just take the MRD-M301 you WILL NOT BE DISSAPOINTED . just for example my friend has 2 of your subs in a 5.4ft^3 boxed giving each sub 150WRMs and DAMN it POUNDS for 150Watts. and mine is almost the same at double the power. so your  350*1WRMS is PLENTY and yours will be at 2ohms bit louder.

Hate too pee on this ..But i upgradded from a w0 to a 10w3v2 pushing about 150 watt's from a 6450 jl amp (at 5 channels)listening to thechno for about 20 minutes i melted the coil's. Had to go give them there sub back. Then i called resonant eng..now i have a sub that give's me dirty look's when i heat it up.   300 for that sub should be enough to melt it...good luck=0.

      thad