Dave,
You have a system that is equivalent to a $1100 Mac Book Pro.. This is directly off the Apple site..
13-inch: 2.3 GHz
2.3GHz dual-core Intel Core i5
4GB 1333MHz
320GB 5400-rpm1
Intel HD Graphics 3000
Now if you want something better under 2k.. I see only two options on the Apple site that I would even consider..
13-inch: 2.7 GHz
2.7GHz dual-core Intel Core i7
4GB 1333MHz
500GB 5400-rpm1
Intel HD Graphics 3000
All of this for 1499 plus anything Apple tacks on after purchase.
15-inch: 2.0 GHz
2.0GHz quad-core
Intel Core i7
4GB 1333MHz
500GB 5400-rpm1
Intel HD Graphics 3000
AMD Radeon HD 6490M with 256MB GDDR5
$1799 Before all the other fees and stuff
But both of these systems use a 5400 RPM hard drive which WILL BE the bottle neck in both of these systems. Personally I would not buy a 5400 RPM drive to put in a system because it kills the performance of the entire system. Hard drives are already the slowest thing in computer systems, Mac or PC. But you can add a Solid state drive to either of these systems.
128GB $200
256GB $600
512GB $1200
If you want my professional opinion... I would keep the laptop you have, wipe it and install win7 64 bit. It will run smoother and it will utilize the 4GB of RAM that XP will never see as well as the dual core processor. I would save my money and buy a Desktop system. With 2k I could build a system that will out perform any Mac as far as hardware is concerned.
Just my $.02
Good luck with the shopping. I'm sure you will be happy with what you decide to do. Personally I would love to get my hands on a Macbook, but knowing the price of hardware, I could never stomach buying one. The Calibrated screens are a plus