My website...
http://klohiq.tripod.com/cars/240sx/swap.html should help you out some. Be aware that the costs can vary quite a bit...just as the hp can so these are just averages and predictions to what you can get out of each motor and how much money the swap/engine costs.
Your other good choices are CA18 and RB25. The other swaps are great engines, but will require more work to install or are used when people are looking for much higher horsepower.
Lastly, KA-T is a great idea if you are on a budget and will offer premium performance at a economy price. Try to get a swap done that will offer 250+ hp for less than 4000.