For those with the a900, how viable is it for use as a walkabout/street camera? I'm at a bit of a crossroads with my "better" system. I am perfectly happy with my DLux4 for casual carry, and have had good luck with my previous DLux3 printing rather large. But sometimes I want/need more resolution, be it for cropping or crop and print large (24x36 or maybe bigger). The thing that I like about my Pentax K20d is the relatively small size and weight, especially with some of the ltd prime lenses. Having a 43/1.8 that weight all of 155g on the fairly small body is great for carrying around town or indoors, and it is fairly unobtrusive.
That said, while I like some of the results I get, I could always use more. There are times when I need to do a radical crop to get what I saw (often when I'm using a small prime and have limited walking tele capabilities). At that point the K20d file starts to give out, and my breath isn't taken away. Well, unless I'm holding my breath. But that is another issue.
The thing that scares me is that I find my 50-135* lens on the K20d to be at the edge of "walkabout" comfort. And that is 685g. The Zeiss 24-70 is 995g. Now part of that may be offset if the a900 body has better balance and a little bigger grip (the K20d is a tad too short to fit my whole hand). I need to try and spend some time with one in a store, but there is no substitute for real user experience.
Also, I tend to shoot very low light. The Pentax files are fine for my taste at 1600 and even up to 2000. I don't mind some noise, as it usually fits the mood. I know that going D700 would get me significantly better low light performance, but I do like the look of the Pentax files, and feel like the Sony may be closer to my tastes.
Any guidance (or push) down the slippery slope appreciated.