I recommend you stay away from the Noble 4A S. I own the Heir 4A and think there's better to be had out there. Contrary to what some say its not a UERM slayer. The DX50, I've had nothing but troubles with that player and only recently got it functioning properly with the latest firmware update. Its sound quality is slightly better then a iPod IMO. Just my 2 cents, you can choose to heed it or ignore it. The decision is up to you.
HERE, hit the link to my YouTube channel. It might be of some use to you regarding making a more informed decision. I personally like the Studio V but its UI is flawed and primitive but the sonics is pretty good. The only other options I've heard/owned would be a CLAS rig or an AK player but those two are pretty pricey so I doubt you would consider them.
Edited by DigitalFreak - 2/9/14 at 10:45pm