Best wide angle zoom lens for my nikon d7k?

Ok I need a good wide angle zoom lens for when i shoot landscapes. I can't decide if i want to get the Sigma 10-20mm f4-5.6 or the tokina 11-16mm f2.8. I would rather spend the around 480$ and get the sigma instead of spending 660$+ on the tokina but i hear bad things about the QC at sigma. I hear that some of the sigma 10-20mm are very sharp but some are soft and dull. Basically what i'm asking is it worth that extra money to get the tokina?

Added (1). I forgot to mention that 700$ is the highest I can go right now.

Tokina and Pentax are now under Hoya. Tokina no longer makes lenses for Pentax. If that would mean Tokina lenses would actually be Pentax made then yes, all the extra money would be very well worth it!

If you're willing to pay as much as $660.00 or more for an after-market wide angle zoom why not step up to the Genuine Nikkor AF-S DX 10-24mm f3.5-4.5G ED for $899.95 from B&H? Yes, the Nikkor is a couple hundred dollars more but with proper care it will outlast you. At least with a Genuine Nikkor lens you won't be worrying about build quality or the manufacturer's quality control.

The Tokina 11-16mm is shown for $659.00 at B&H.

B&H - http://www.bhphotovideo.com/...ovideo.com

NOTE: In my opinion a good sturdy tripod is mandatory for landscape photography.

The Tokina is the best ultra wide angle out there - even out performing Nikon's own offering. Get it if you can afford it.

As for the Sigma - I have the 10-20mm and it's tack sharp, no issues to report here. I got the Sigma because at the time I couldn't afford the Tokina AND it was on back order everywhere in any case due to its popularity.