Thoughts on upgrading to a DSLR - EOS 400D or K100D?

I've had my Powershot A95 for a year now, and while I've certainly enjoyed using it (and I've used it a lot; my ~1400 photos on flickr are evidence of this), I've been running up against its limitations. For indoor portraits, it's not sensitive enough to take a short enough exposure without using the flash, and its flash invariably causes horrible redeye, not to mention the harsh shadows and unnatural flat look caused by direct flash. So my only really good shots of the kids have been made either outside with clouds diffusing the sunlight or inside when I can herd them to a room where sunlight happens to be shining through the window. Even with bright afternoon window light, I still have to crank the ISO speed to 100 or 200. In an ordinarily-lit room, with the lens wide open and at ISO 400, the needed exposure time is usually on the order of 1/15 to 1/10 of a second--which, with a tripod and a subject that can hold still, is passable (though the pictures will be very noticeably noisy). But with hyper little kids, it's out of the question. This limits my possibilities in taking good candid shots.

I should also mention astrophotography. My A95 does surprisingly well considering it's a compact camera--I've even managed to take a few half-decent photos of the Milky Way. With a single shot, taken at f/2.8, 15 s, ISO 400 to let in as much light as possible with my camera, the Milky Way only barely registers. Brightening it only brings forth a mess of noise. But several shots added together to increase the signal-to-noise ratio produce a half-decent photo. Here's the result of 16 such shots added together:



It's still pretty noisy. Noise reduction software can help a bit. But what I really need for this type of shot is a more capable sensor. My first thought was to get a Canon Rebel XT. Its 8MP CMOS sensor at ISO 1600 has noise levels comparable to my A95 at ISO 200. And its exposure time is not limited to 15 seconds. With the kit lens, it'd take in a wider chunk of sky too. The bigger sensor also allows artistic depth of field effects (blurring the background of a portrait in order to bring out the subject).

A DSLR is definitely the way to go for highest-quality photos, but it has some cons as well: DSLRs are expensive and bulky. Interchangeable lenses yield a lot of possibilities but cost individually as much as a compact digicam. Pictures must be composed through an optical viewfinder, which is not nearly as handy as my A95's flip screen LCD, although it's probably a plus when it comes to focusing through-the-telescope, where the digicam's blocky LCD makes accurate focusing difficult.

I've saved up $1000 for the purpose of buying a DSLR (actually, it was originally a telescope fund, and I've waffled a bit on how I want to spend it). A few months ago, Canon was running a $100 rebate on the Rebel XT, and I seriously considered buying one, but that model was showing its age, so I decided to wait and see what Canon had up their sleeve this fall. I already got bit by this last year, when shortly after I bought my A95, Canon announced the A610/620, which answer all of my gripes with that camera (slow AF, purple fringing, lousy movie mode) and add a longer zoom and bigger LCD, not to mention the custom timer mode--I seriously considered upgrading specifically for the ability to have the camera take several shots on one click; it'd take the effort out of shooting constellation stacks and it'd eliminate the need to run back to the tripod between family shots.

So anyhow, Canon's new Rebel XTi (aka EOS 400D) has been announced. Its new 10MP sensor is interesting, but slightly worrisome; since it packs more pixels into the same space as the old Rebel's 8MP sensor, it could decrease light sensitivity and increase noise. Canon says they've reduced the space between microlenses to compensate, and the new sensor is a match for the older one despite its smaller pixels, but I'll have to see that for myself when dpreview.com and dcresource.com get their reviews online. The dust removal feature looks interesting but not compelling. The improved autofocus (borrowed from the 30D) addresses a common concern about the Rebel I've read in the forums and IMHO is the only reason to consider the XTi over the XT.

I'm also seriously considering the Pentax K100D. This camera costs less than the XT, and is in stores now, but is still new enough that it hasn't been reviewed by dpreview or dcresource. It has several advantages over the Rebels:

• In-body CCD-shift image stabilization (works with all lenses, but is an expensive per-lens feature with Canon)
  
• Larger, brighter viewfinder (good for manual focus on stars)
  
• Accepts AA batteries, NIMH rechargables are much cheaper and more easily available than Canon's proprietary Li-ion units
  
• I like the status LCD on the top. The XT puts in on the back, and the XTi gets rid of it altogether
  

Its cons are:

• Less resolution (just 6MP)
  
• Poorer high-ISO performance (though I have yet to see a direct comparison)
  
• Slower AF (though this is still anecdotal since the big sites still haven't posted reviews)
  
• No cheap fast prime lens like Canon's 50mm f/1.8 is available (if I get a Rebel, I'll get one of these for indoor portraits)
  

At least the K100D seems (still, anecdotally) to have fixed the lousy JPEG processing of the *ist series. (I actually considered getting a *ist DL--it offers unbeatable value--but my main turn-off was the stupid name.)

So anyhow, that's where I stand. Whew, that was a lot longer than I thought it would be. Thanks for reading my novel, if you've read this far. :)