Suggestions on 12 sub

I have a JL 12W3D-2 sub in my truck. The box that it is installed in is about 1.25 cuft sealed.  It's not exactly enough air space for that sub, considering that sub would sound good under about 1.5 to 2 cuft.  If i switch that sub out for either a JL12w1-v2, Memphis, or an Eclipse in the same range as the w1-v2, would i get more spl and sound quality, or should i just stay with the W3?  The spl and sound quality arent that bad with the W3, I just thought that I would get more than I do, and I figure that the reason is the box.

why not build another box for the w3? what kind of power are you giving it? i know the sq and spl was great for my w1v2 and i had that thing with like 120-175w in a ~1.6 sealed box.. i always wanted to try it ported!

Its getting about 300 watts, and the reason I don't want to build another box is because I don't have any room in my single cab truck for more than the box that I already have.