So im thinking on what to do with my $600 i already have 2 M2 level 3 15s and i was thinking about buying 2 more (i would have 4 total) BUT they would only be getting 250-300rms per sub my other choice was 1 XL M2 18 getting 1150-1200rms i know i would have more cone area with the 4 15s but the 1 XL M2 18 would be getting alot more power what would be louder in your guys opinion the XL M2 18 would be in 6.2 cubic feet tuned at 33hz ported and the level 3 15s would be in 12.1 cubic feet tuned at 33hz ported of course