I've spotted a Sigma 18-35/1.8 lens, that is slightly more expensive than the Tokina 11-16, but gives access to the non-ultra end of the wide-angle.
There are also a few third party 16/2 primes, that may well be "good enough" and fit with your other lenses.
And then there's the Zeiss Distagon....yeah never mind
I myself have the Tokina 11-16, and it's quite wide, even at 16mm.
What I'd like you to figure out, biostud, is whether you want a zoom or fixed focal length lens. Given that you have two fixed lenses already, I would say that adding something fixed would make sense - but that's a principal decision you have to make. I assume you will have to get a DX/DC/whatever lens, as 35mm compatible lenses cost around 4 times as much as the smaller ones. Even an 18/2.8 or 20/2.8 is going to cost more than the lenses you listed, especially new.
Wide angle (non-fishy) DX primes are few and far between: A Samyang/Walimex 14mm/2.8 and 16mm/2 are pretty much the only ones I found - might be available under a different brand in the US. Still, they're cheap and apparently not unusable.
In the end, almost any lens will be good enough to take good pictures with, especially those you listed - decide on the specs. Especially minimum focus distance is important with very wide angles - if it's too far you can't always get the composition you want. UWA is the best kind of lens for near-far compositions --- I'd go so far as to say, that it's pretty much the only thing you can do with them. Beyond 16mm has little use for landscape, for example - you get little to no detail, and a lot of sky - and that pesky sun is always trying to get into the frame
