If you've got $5,000 to spend then you've got several options. You could buy a GSR swap, and depending on whether or not you can install the motor yourself, possibly have some money left over for bolt-ons (intake, header, exhaust, etc.). You could do a an LS swap, and probably have some money left over to spend on bolt-ons, maybe even a turbo kit. Or, you could buy a nice turbo kit for your D16, and make more power than either of the two afore-mentioned swaps.
The advantage to the swaps though, would be that you have a better platform to build on. A turbo kit on a B18C GSR is going to produce better results than a similar setup on your stock D16.
How much power would you ideally like to make?