I am planning on buying my first, but I need a little guidance.

I was pretty set on getting a Canon Rebel XS, but I started to look at some Nikons and I'm not so sure anymore...

Any suggestions or tips before spending my money?

Yup.

Think long and hard. Really decide if you need a dSLR. Because those, just like the point and clicks, will become outdated models.

I have a Pentax 6 MP with 3 or so lenses. The model is no longer made and the models that came after it are soon to go as well to make way for the next.

Been contemplating selling it because to be honest, I just grab the little Nikon point and shoot instead. Lugging around a camera bag and all the shit that goes with it just gets old.
And when they get high definition commonplace in P&S cameras along with a full-frame sensor and the 12X optical zoom like some models already come with, You'd be hard pressed to tell the difference, I bet.

And if for artistic merit, it was that important to you, you'd be shooting with medium format instead anyways,

For me, I'd rather sell my dSLR and use the funds to buy a flash card based camcorder (So damn tiny) and use the Nikon for now and upgrade to another model down the road.

You'll find you're going to take far more candid photos than artistic ones and the dSLR most of the time won't be with you because, once again, it's just not convenient to lug around everywhere. Honestly, I've used mine maybe 4-5 times in the almost 3 years I've owned it.
The P&S camera has seen alot more action.

Check to see what's going on in the digicam technologies and make a sound decision from there, would be my advice.

Do you think this would pass muster for what you want?

http://i44.tinypic.com/w1el94.jpg

And yup, the litle Nikon P&S (L-18 cheaper model) took that. They're only going to get better too.

This is making everything so much harder.

One of my big reasons for upgrading to an SLR was their versatility. I love fisheye and different colored filters any p&s wouldn't satisfy this.

I currently shoot with a canon powershot sx100 and its a pretty good camera, but it still leaves me wanting more.

Try Canons and Nikons out in the shop, and see which ones you like the feel of most. I'd say you're probably best to steer clear of Sony Alphas because they're a bit crap and the lenses stink, but Pentaxes are great value too (and you can get tons of old lenses for them), and the Olympus E-series SLRs are tiny, which I like (despite the tiny sensors).

Canon and Nikon are ultimately not a great deal better than one another, but are still a better bet than any of the other manufacturers I would say. As I said, go try them in the shop and decide which one feels easier to use and more intuitive. I prefer Nikons, but that's just me - there are plenty others who prefer Canons.

As for the DSLR vs. P&S debate, I'd say it's a total no-brainer to get a DSLR if you actually want to really get into photography. Sure, a P&S is a bunch more portable and subtle, but you'll miss a lot more shots due to things like shutter lag, focus lag, and poor low light performance. You might get similar picture quality in daylight on a still scene, but if you want to capture things that move, or shoot at night without flash, then DSLR is the way. I have a P&S camera as well as my very big and bulky Nikon D700, but I prefer lugging the Nikon along 98% of the time. The only reason I really use the P&S camera is that it has a waterproof case, and I can take it places where I wouldn't wanna damage my Nikon, like in the sea for example :P