121A replacement

I am currently using a B212, which I have replaced the 75W amp with a 150w plate amp. This sub is used in a 5.1 setup. With twice the wattage I really get a lot more kick for the soundtracks. But when large explosions occur the voice coil will extend to far and then I have to put a small amount of pressure on the dust cap to get the voice coil back in the gap. The amp is set at 1/2 volume.
So want would be a good replacement for the 121A driver, that has a long throw, to prevent this from happening?
I'm also thinking about building another sub using one of my LE14As so I can have two subs in the setup. Will the LE14A have the same problem as the 121A with a 150w or larger amp?

I use a pair of Le-14A subs in 4cu.ft. boxes. I am going to build a third for my LFE. I use the Partsexpress plate amps and have never had a problem even at very high levels. One thing to remember is they are limited x-max wise 5mm so I use no low end boost at all run them flat. My LFE will be in a smaller box so I will have to use some but I would keep it limited. The 14H would be better if you can get your hands on them.

Rob:)

I should have stated my original post differently. I'm not looking to get rid of the 121a. I should have asked what I needed to do to correct the problem. Which you did in your first reply, that has vanished. I wasn't even thinking about needing a filter at 20htz.
The sheet that came with the plate amp has instructions for modifying the EQ. Changing two resistors to raise the filter Fc from the factory setting of 14htz.