I've used the VLD3 for the past year. It's velcro'd to my PA500. It sounds nice. And I picked it up on ebay for $99.

The controls are easy to reach (except for the output volume on the back). The optional 3 switch foot pedal is helpful. I use the doubler with reverb while singing, and add in harmony parts as needed. The indicator lights make it easy to see what the settings are.

Prior to this unit, I used a Helicon Harmony M for a year, and a Digitech Vocalist Performer since 2001.

Guitar Center has a used one for $149 http://tinyurl.com/7myrune

Duane