No problem xerxe,
Well I use a midi keyboard and a headphone out to for my piano, But that will soon be connected to the objective 2 amp.
And yes try out the amp on the U7 first, Mine gets loud but I want to avoid turning volume up in Kontakt.
Also I have been searching for something like you are, I didn't want portability, just quality.
That is where I found the Objective 2, JDS supplies the USA and Epiphany supplies the UK, But I got mine from a guy in the UK who builds them at a much higher quality and look to the other two company's.
What is great about it is that it's meant to be plugged into the wall for full functionality, or it has two 9v batteries for portability (6.5x gain doesn't work on batteries but holy hell that would be loud) for 10+ hours battery life. So it's kinda like the best of both worlds. Check out the specs on it. I got mine for £85 delivered.
Im still trying to decide if my U7 or my headphones are faulty because I have never had semi audiophile equipment and don't know how it should sound :/