Best general purpose lens(es) for Canon under $500?

OK, after a month of hemming and hawing, I think I've finally made a decision. I think I want to get the Sigma 17-70 f/2.8-4.5 DC Macro and Canon's 50mm f/1.8. The Sigma's gotten pretty good reviews:

http://www.photozone.de/8Reviews/lenses/sigma_1770_2845/index.htm
http://www.slrgear.com/reviews/showproduct.php/product/349/cat/31
http://www.photodo.com/topic_65.html

and it just seems like a sensible choice as it's relatively inexpensive (about $350), covers a wide focal range sharply, has some macro capability, and has some lower light ability. Seems very versitile and considering my upcoming responsibilities in life around mid-May... I don't think too many expensive lenses are in my future. It seems to me this lens could do a lot of the interiors/groups/landscapes/nature photography I'm interested in, and the Canon 50mm would be great for portraits, and that's basically all I want to do. I have a crappy telephoto zoom lens I can use as long as I want, and considering it's not a priority that lens is fine for now.

Does anyone have experience with this lens? Any recomendations? In my long deliberations I've also been looking seriously at a few other lenses, mostly used from KEH so cheap, like $100-200:

Tokina 19-35 f/3.5-4.5
Sigma 17-35 f/2.8-4
Tokina 20-35 f/3.5-4.5
Canon 20-35 f/3.5-4.5
Tamron 20-40 f/2.7-3.5

Tamron 17-35 f/2.8-4 (new, more expensive)

and if I don't buy the Canon 50mm (at least soon):

Tamron 17-50 f/2.8

Any advice? Should I go for it and pull the trigger on the 17-70?

Engaging in the sin of bumping my own unpopular thread... I'm still hemming and hawing. I bought the Canon 50mm f/1.8, and now I'm trying to figure out what to do for the wide end. I'm still basically thinking of the thoughts above, but getting a used Tamron 20-40 f/2.7-3.5 is tempting on the being responsible and not spending a lot of money side.

Does anyone have any experience with the Sigma 17-70, Tamron 20-40, or Tamron 17-35?

Any recommendations for a different wide angle lens under $400, used or new?

I do like the idea of getting an ultra-wide angle (given the Canon's crop factor). And I think I can live without the 23 or 25 to 49 range pretty easily by moving my feet or cropping. But it also seems like people hold on to these lenses and that the used prices aren't too much better than the new prices.

Which probably means they're pretty good lenses eh?

Maybe I should return the Canon 50mm f/1.8 and get that Tamron 17-50. It does look nice, but at $450 I don't think I can afford it. Including a UV filter and the Canon 50mm, that would put me well over $550 total for lenses.

I want to have a great camera for portraits and family shots for when my baby is born in May, but those pictures aren't going to be so lovely if we're starving and living on the streets...

Obviously I'm exaggurating. But a line has to be drawn somewhere as to what's too much.

I'm having one of my days when the Sigma 17-70 is calling to me. And it's almost $100 less than the Tamron 17-50, although the Tamron is f/2.8 and much better at 17mm...

yarg!

I realize that there's differing wisdom on this, but I think with my conditioning I'd have to put some filter on the lens to protect it. And I thought that putting a cheap, crappy filter on an expensive lens kind of defeats the whole purpose.