Which DSLR camera should I invest in?

I having been taking photos of people for about a year now and am looking to upgrade my camera. I don't claim to be a 'Professional' but I do understand that it isn't necessarily the equipment that makes a good photo, but the skill. On the same note, though, I would like a camera to take more clear photos than mine does now and one with a rechargeable battery. Therefore my question is, Canon, Nikon, or make a suggestion.
I'm not looking to go over $1000. Probably closer to $600 so I can get a separate lens also.
I take mostly portraits but also like to play with other concepts.

Any of the top makes produce good DSLRs… Canon, Nikon, Pentax, Sony, Olympus… Take your pick!

Shop around in the computer cause i paid too much for my canon rebel.xsi yet i still gotta deal on my two lense kit… But then i found places sold it for even less.naturally…

Ultimately, the first question you have to answer is: Canon, Nikon, or other (i.e. Olympus, Sony, Pentax, etc.).

Canon and Nikon dslr systems are quite similar, with lots of overlapping models. You can find good comparison reviews between specific models here: http://www.h2hreviews.com

In the end (having read through thousands of reviews prior to making the same decision a number of years ago) is Canon has better image quality (particularly in low light), while Nikon has better mechanics (principally autofocus and metering accuracy).

The lenses are very comparable, so I would ask which you feel you need more off hand - better low light performance or faster autofocus.

I went with Canon for the low light image quality, though I do long for Nikon autofocus constantly!

Hope it helps.

You will have to do some comparison shopping. Cameras are a very personal choice

You can't really go wrong with any dSLR.

Not sure what you mean by "more clear photos", but if your unclear photos are due to human error (rather than to the limitations of your current camera), then getting a more expensive camera won't help you.