Its definitely an awesome combo!
Btw, I see you're a fellow BlackBerry User! So rare to see one haha, I use a Z30 myself. I don't know if you are aware of this but blackberry phones are capable of true variable line out. Attach a headphone to the lead and change the volume of the phone. The top of the phone screen on the status bar it should show - headphones volume and volumebar
If you attach the leap to an amp using a 3.5 mm line out cable and try changing the phone volume, notice what it shows on the phone. Line out Volume and volume bar showing your current volume Ergo variable line out, so its not double amping! I plan to use my Z5 this way, phone to amp to Z5
It works on my Z30 so it should work on your Leap as well. The Z30 does usb audio out, and it work with my FiiO E17 perfectly. if the leap supports OTG give it a shot!
Sorry to be so OT but I thought I should mention it!