Digital cameras: opinions: SONY W170 or CANON SD950/890/770 ??

opinions: SONY W170 or CANON SD950/890/770 ??

Hello! So I'm looking for a camera to replace the Canon SD700 that I no longer have. I adored that camera. Before the sd700, I owned two other Canon cameras. I am open to other brands, but I feel comfortable with the Canon brand.

This is what is currently important to me:
- size (ultra-compact)
- viewfinder - while these are usually somewhat inaccurate, i sometimes I want to sneak pictures without people noticing. also, I find a viewfinder helpful if I know that I'm going to run out of battery soon and want to conserve as much power as possible while still taking pictures
- photo quality, especially in low-light conditions - i know that compact cameras don't take the best quality pictures. But given my restrictions, i am looking for a camera that will produce the highest quality pictures possible (vivid colors, sharp/crisp, low noise). I prefer not to use a flash when possible, so excellent low-light abilities are important to me.
- build quality - i would like for it to hold up over time

SO, I've narrowed my list down to these four (in no particular order):

Canon Powershot SD770 - This camera is both less wide and tall than my old SD700 -- but it is slightly thicker. But... okay, fine, I think the back is kind of ugly and that I will miss having a rotating wheel. I'm having some trouble finding extensive reviews on this one.

Canon Powershot SD890 - I've read that it's an upgrade of the sd850, which was an upgrade of the sd700 that I so dearly loved. That said, the plastic body is a bit of a turn-off and it is oddly shaped. Also, given its dimensions, it is slightly larger than the sd700. I was hoping for something a tad smaller, but I suppose that's a minor complaint. It's still ultra-compact.

Canon Powershot SD950 - Well, I don't need 12 MP. The camera seems to have all I want (and in some cases, costs less than the SD890), except reviews complain of lag time. The camera seems slow and is larger in every way than the SD 700, which makes me hesitate. However, it has the largest sensor of the bunch--which means better image quality/less noise (or am I completely off base)?

Sony Cybershot DSC W170 - I've only used Canon in the past, so I added this camera with some hesitation. I think the camera itself is beautiful. Although taller and wider, it is also much thinner than the others. From what I've read, it has received good reviews. Maybe I'm crazy, but I find that cybershot pictures turn out more vibrant than those from a canon. I've been having trouble finding reviews that discuss its photo quality, which is an important quality to me (I found one review that calls its photo quality "decent," which isn't great considering the Canons are almost all lauded for their "excellent" photo quality).

Of these four cameras, which would you choose and why?

Have I overlooked any that fit my needs?
I recognize that by insisting upon a viewfinder, I have substantially limited my choices. Maybe a camera like the Canon SD870 or SD790 would be better for me despite the lack of viewfinder? Maybe having a viewfinder isn't as important as I think it is? I don't know, I feel torn in that respect.

Thanks!