P&S superzoom vs SLR zoom?

[mhdick]

I didn't really know where to post this, but I thought it did figure into techniques...

I currently have a canon SX10is (20xzoom) 10 MP P&S.
I do like it for the most part. I like the zoom for taking pictures of deer while outdoors - sometimes from a long way out (have one picture at 1/2 mile on FULL 20+4x digzoom - not super quality picture, but it was fun to do).
However, I am frustrated with being unable to get any DOF in my pictures of my 11month old, HAVING to use the flash indoors - or just have crappy pictures (or use the flash and have many blown out). And, full zoom only really works in very good light.
I'm considering a new SLR - beginner to mid-range type. NOT the $1000+ cameras! (maybe Pentax KX with lens kit 18-55mm f/3.5-5.6 AL and 55-300mm f/4-5.8 ED Lenses) Or, for the following questions figure and similar SLR and similar lens (up to 300mm f4-5.8)

My main question is this: How close will a 200mm zoom (or 300) compare to the 20x zoom on my current camera? Not only actual zoom, but picture quality in varied situations. Also I would assume I could crop better having the SLR and a zoom, where cropping from a full 20x on my P&S doesn't work much.

please let me know here if I'm close on my math: my 20x is up to 560mm (35mm equil per canon website). On most mid-level SLR's, the 35mm equiv is the lens x 1.5 (depending on camera) - right? that would make a 200mm zoom equilavent to 350mm and 300mm to 450 (which is less than the 560 on my canon)?? If so, (and I know - depends at least some on quality of lens, use tripod...) what are thoughts on quality of shots with both zoomed out? Or, is this pentax zoom to slow for my desires??

My uses would be wildlife and sports photographs (NOT pro, but personal use). Mostly 4x6 photos, with occasional blow-ups. Sports stuff could be indoor HS bball, vball, etc and some outdoor sports anytime during the day. Also around the house & other activities of a 1 year old...

hope I haven't rambled on too much to answer this decently.
thanks in advance.