$10,000 for New Equipment

Time to upgrade to the 20D.

that's $1,500USD.

I have $8,500.00USD left to spend on equipment, including 2 lens', battery grip, and Studio Lights...

Got plenty of memory cards...

Now the question is not what kind of lenses and lighting should I get with this budget, but what would YOU get?

Mainly for indoor nightclubs and events and outdoor headshots and portraits. So I'd definitely need a fast lens, and a mobile light setup...

Thanks for the input guys!

With a $10K budget for the things you mentioned, I think I'd get a 1D Mk II instead of a 20D, 35mm f/1.4L, 50mm f/1.4, 85mm f/1.8, 135mm f/2L, Tamron 17-35mm f/2.8-4, Canon 24-70L, 70-200 f/2.8L IS, 580EX, Alien Bee DigiBees. The primes will give you the speed you need indoors.

^^^ what he said, and the vertical grip is built into the 1DMk2 body.

85mm 1.8 & 200mm 1.8

85mm f/1.2L
135mm f/2L
35mm f/1.4L

That's all you need.

With the $8500 you have left and showing what you have on you signature.
I would get in order after the 20D
a 580EX flash (to go with your 550EX)
a 85/1.2 (slow to focus, but that extra bit of aperture may make the difference)
a 70-200/2.8L IS (If they let you use a flash, you can stand back and take shots from across the room)
Then the studio lights; an alien bee setup with a vagabond CU-300 battery.
Followed by a radio control for the flashes (pocket wizard or alien bee) (no wires needed)
a portable storage device like the P2000.
then the 16-35/2.8L (or can substitute a third party f2.8 wide angle zoon)
the 50/1.4 and/or 35/1.4 (for close up no flash allowed)
and finally a new bag or two to put it all in.

That is what I would get if I were shooting what you are.

Just my opinion,