First of all why do you want puppies? They may be cute, but you cant keep them all? To do it right, breeding is an expensive undertaking as you 'should' go through all the health checks for your breed, but with a cross breed you could be doubling up on any hereditary problems.
Speying may not stop her humping your cushions. One of mine who is spayed used to have a lovely easy to care for coat, but now is more like a woolly yhett - the vets wont tell you it may change the coat texture and make it difficult to manage. However as Pastafreak has pointed out, you do have the advantage that you dont have the worry of a pyo
This is a good read.
http://www.dogbreeder...fSpayNeuterInDogs.pdf