The advantage no one as discussed yet, is that currently he is analog in to the H120, and with adapters he would digi into the H120. In other words he is moving from the H120 iRiver A/D to the UA-5 A/D, and I would think that would be better. $140's worth of better? Probably not. But it is a difference, and it will probably have a different flavor, which may (or may not) be appealing.
If you are "itching to do something", I'd say keep the AT > 9100 > H120 system the way it is, and start thinking about big mics to go in front of the UA-5.