Not super happy with JL 12w3.. Looking for another 12

The box has 1.3 cu of airspace which is slightly large, but right now the sub is running maybe 180 watts if even and it still bottoms out if I push it.

I would like a sub that I can run 300 watts through all the time without it bottoming out. Now, while I do know my sub is good and the box is too big, the problem is that I am having trouble selling just the box. So selling the whole shebang will be easier to do. While I'm at it, I'm considering other brands but don't know what's good. I've been told Memphis is good. Sorry about my lack of a precise use of RMS, but that is what I would like to run it at, so the sub needs to handle 250-350 RMS. this one I believe is optimal at 250 RMS so I'd like my next sub to operate well with a little more power, closer to the higher range of output my amp can handle.

I know the JL can handle 500 watts however that is very close to its maximum range.

On another note, my alpine amp has a gain control knob and when I turn it from say 0 to 1, the sub makes this odd grinding noise. Anyone know what that is? It doesn't do it when I turn the knob from 1-10. Only 0-1.

What about this? It seems to like a smaller sealed enclosure and has a 750 watt RMS rating, which means it should have an optimum RMS of around 400 which is the max my amp can put out.

Image Dynamics IDQ12 V.3 D4 (IDQ12-V3D4) 12" Dual 4 ohm IDQ V.3 Sub

I'm not entirely sure what I'm hearing, I'm going to the local audio shop tomorrow to have them check it out.

As far as my amp, it seems to be powering the sub just fine. My gain setting on the sub is super low. If I try to push it towards 300 watts at 4ohms my sub starts to bottom out horribly bad, I'm assuming because the box is entirely too large.

The amp is an MRX-M50.

After going to the audio shop, the guy told me two things. One, the noise that my sub makes (grinding/crackling noise) when I turn the rux-knob from 0 to 1 is a disconnected voice coil and that I should send it to JL for repairs. He also told me that something else must be wrong with the sub, because he said "JLs like being in big boxes" and that I should be able to crank the gain up a lot more than 40% (130ish watts) before it bottoms out. He thinks it shouldn't be bottoming out so easily. He also said he used to have two W3s.

So, send it back? I guess he may be right, because the box is really only .175 larger, would that much airspace make such a drastic difference? I guess I need to send it to at least get the voice coil fixed.

I was thinking about taking a circular saw to the box and cutting it down 2" on each side. But I need to find someone with a big enough saw. Haha

To answer y'all's questions:

The sub bottoms out the worst during very low kick drum style notes. The sub is also 4ohms so that's what I run it at on my amp since I only have the one sub. As far as settings, I'm not sure what I am doing wrong. The bass sounds good, but I can't crank it. My head unit has an internal amp, but that doesn't affect the sub, does it?