Upload & Sell: On
I'm going to suggest a different approach here, rather than see you just spend your money and grab some gear willy-nilly. While it is possible to do portraiture with a wide-variety of equipment, I get the impression from your post that you are looking to attain specific results. And, taking the time to look into that, and seeing what others have been doing before you, might, I suggest, help you narrow down your considerations. To that end, perusing both the People Photography and Wedding Photography boards here at FM will open you up to a wide variety of shooting styles, lighting considerations and, yes, equipment choices.
Methinks that just spending (at least) a few days on those two boards should help you see what sorts of portraiture shooting you'd like to accomplish. And, FWIW, your question would likely gather more attention and responses than over here on a "gear" board.
Your budget has already pretty-much eliminated a full-frame body from consideration. So your choices are down to an older 1.3x-crop 1D-Series with EF-only lenses (I'm assuming you're looking at the Canon line here) or a 1.6x-crop xxD-Series (xxxD?) with either EF or EF-S lenses. What then? Zooms or primes? Do you have a preference? What have you been using on you 10D? What focal-range have you found you like using most to accomplish what you'd like? Understanding even just a bit of this may well help you decide between, say a 1D-body with a few fast primes or, say, a 30/40D and a fast EF-S zoom...or any other combo!
I think these days are a great time for anyone starting out with digital photography...being able to get one's hands on older, technologically mature, pro-grade bodies is just a fantastic position to be in! And, for you, living in Chicago, where I'm certain there are more than a few camera shops around, I'd bet you can even find yourself some nice "beater" L-glass to slap on that, um, "new" body! For a fraction of the cost of what some "Pro" paid just 5 or 6 years ago you can be "rocking" some nice gear and grabbing some great shots.
Of course, you might just want to say. "the heck with all that!" and go grab a 1D IIn and a used 24-70mm f/2.8 L and go out shooting today.
Hope this helps, and welcome!