I guess you have never stated what type of accuracy you want to control you speed. That information is part of what dictates what type of valves and other components you should be using.
Here is a lower end controller but your speed feedback will have to be 4-20 or +/-10V:
http://www.hctcontrols.com/products/dr/drf.htm
The valves you are using are generally lower performance valves compared to state of the art hydraulic motion control.
If you don't really need a lot of precision, you may get away with a pressure compensator on your valve. That should keep the pressure drop across the valve constant regardless of the load. It's not super accurate but might be "good enough" ...