As the proud owner of a Canon 550D and among other notable lenses, the Canon EF-S 10-22mm f/3.5-4.5 USM is just plain awesome. It's a creative lens, and that's why the uneven gradient caused by CPLs don't seem to bother some photographers.
I'd encourage the original poster to purchase the 10-22, and then consider filters after he or she has had a chance to really figure out the best way to use it. For example, in the OP's second (middle image) I might have moved more along the ridge, used the 10-22, panned up and to the right a bit to capture the ridge line with the clouds.
However, don't use ebay. Use the "marketplace" section of this forum or FredMiranda.com's bull/sell board
. This way, you'll be connecting with other photographers who take care of their equipment and you'll have a much smoother transaction. Plus, if you decide the 10-22's not for you, you can sell it back for about the same price you purchased it.
OP, post some photos once you've used your new lens!
Regards, RTMoore