$5000 for a quality rebuilt s14 is a reasonable price. there are some things to consider, you will need to have a 265 tranny or be willing to modify the bell housing to access flywheel sensors. if you maintain the injection system, you will need to mount the ecu and route the airbox on the battery side of the coupe. there are individual throttle bodies which stay sinked - better than weber dcoe carbs. this engine in stock form achieves 192 hp. with changing the intake cam to a motorsport 264 and evo 2 spec you can move it toward 225, and with going the full evo 3 route - including a 276 intake and moving the 264 to the exhaust side - 240 hp is achievable as a 2.5L ... but you will have to make sure you have enough fuel flow. these are pretty robust engines
i will caution you that these engines will add significant vibration to any bmw, they are relatively high strung, but very reliable. for those that are not familiar with the engine - there is no onboard thermostat - it is three hose mounted in a canister between the water pump, the reservoir and the radiator. the vibrations tend to loosen some of the intake sleeves to the valve cover / cam box and create lean conditions. this engine has no knock sensors and lean conditions kill these engines. btw, you will also have to run the cooling system at higher pressures.
a transplant w/ this engine is not for the faint of heart ... but will be exciting. anybody interested should read Dave Varco's M2 transplant site
http://www.2002parts.com/html/m2_kit.html
it would be an exciting idea for a 2000cs though
