wide angle zoom

Hi,

I have a 60D, and my primary lens is the 24-105L.  Even though it's not so wide on a crop sensor, I really love it's range and quality (I wish I could afford a couple more 'L' lenses, but alas ...).

So I'm looking for -- maybe just daydreaming about -- a complement to it for situations where I could use a wider lens.  I'm thinking mostly of indoor family shots but also for general shooting in tighter spaces.

It seems like most people love the canon 17-55 f/2.8 (expensive), sigma 17-50 f/2.8, or tamron 17-50 f/2.8.  But I feel like, while those give me just a little bit more on the wider side (and are one stop faster), they mostly overlap with my 24-105L.

Canon has a 10-22 f/3.5-4.5, sigma has a 10-20 f/4-5.6, and maybe there are others that would give me even a wider angle and not overlap at all with my 24-105.

What do people feel about one of these as an option?  And how come there's no lens in that range -- or is there? -- that's faster and has a constant max aperture??  Does anyone else use this kind of combination of ultra-wide + 24-105?

Thanks,

-ira