I doubt if anyone has made a 16mm lens with an aperture anywhere near as wide as f/1.4. f/2.8 is the largest aperture one ever sees on a lens that wide (eg, the Zenitar 16/2.8, or the Pentax DA14/2.8). But it's rare to need that large an aperture when shooting that wide. Are you sure you'd really need a lens that wide in the first palce, though? That's wider than your 18-55 at the 18 end. And note, at the 18 end, the 18-55 does f/3.5, which is almsot as good as f/2.8, so there really isn't much to gain in the speed department by going to a different lens for wide angle.
BTW, there are far more than two 50/1.4's, but the Pentax FA50/1.4 is probably the best for the money if you limited conisderation to brand new lenses with autofocus. There is also a DA*55/1.4 that is better but much more expensive. However, if you can deal with manual focus, then there are *tons* more options for *much* less money (eg, an M50/1.7 that typically costs about $30).
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