In order to answer your questions it is critical for you to know the year of the crx, specifically becuase the 88's and 87's are very different.

I don't know about converting it to power, but I can tell you my 87 Si is fine without power, and I also like the fact that power is going to the road and my gas mileage, and not to help me turn the wheel which is very easy in such a light vehicle I think.

There are many many engine options available, but this is one thing that is dependent upon the actual year of the vehicle (and make?).

Give us some more details if you can so we can help you out, thanks.

have fun!