If quality is more important to you than cost, imo Red Jacket or grundfos are top of the line. Submersible's and jet. Both companies offer different lines and models, depending on the quality. The impellers will go out before the motor will. A higher end pump will always have stainless steel impellers. As far as pressure, 60psi is plenty. Most houses have 40/60 pressure switches. Pump kicks on when the pressure drops to 40psi, and stops when it builds up to 60. 40/60, 50/70, 60/80 are all common. 60 will feed a large three story house nicely to give you an idea. 1/2 horse is about the norm for a motor. Larger depending on how long of a push it has from your source, and diameter of the line also. You can look on the pump to check how many gpm "gallons per minute" it will push. If im understanding your situation, you might need a beast. Any pump will get the water to your garden/gardens...but if pressure is a big concern, crunch the numbers.