At that price point and given your stated intentions, and what I deduce about your personality from the description.
I recommend one of:
Canon 30D (just over $1000, but with rebate very close)
To my mind these are the first of the "proper" cameras. They are hefty, built well, handle excellently and have excellent picture quality.
All 3 systems give excellent pictures, for a relative beginner you might as well say the quality is identical between the 3.
The most important differences between the 3 cameras will be how well they fit in your hand and how good they feel. If you have even a vague preference for one brand then by all means follow your heart.
If you think this is likely to be a long-term hobby then you may want to push the Pentax into 3rd spot. And if you think you are likely to want to upgrade and upgrade in years to come you should probably push Canon into 1st place.
If you think that this is likely to be as good as you will want (and all are very good indeed) then the Pentax is probably somewhat better value because of the in-body stabilisation. With Canon and Nikon you have to pay for the stabilisation in the lenses.
I was in a very similar position a little over 2 years ago and went with the Canon 20D. At the time it was a class leader, but now Nikon and Pentax have caught up to the 20D/30D.