I have one MP40W driver left up for grabs for $30. I upgraded to the ES models a few months ago. It has the latest Gen 2 firmware loaded, so that means night mode, long pulse and a few other features. If you'd like to upgrade your MP20 this is a good start, although you'll need a power supply with the driver to upgrade.
Here's a photo to avoid confusion as to what's for sale. One driver shown with the cover off. You'll need to transfer the dry side pump cable from your existing MP20 driver to this driver. And you'll need a 24 VDC, 2.5A power supply.
