I'm just wondering if this is enough to run a U25 pulling just a couple of cars. I have a trackside mounted in a battery car to power my Dash-9. Also, I assume the U25 is set up for battery like the D-9. Just planning my Christmas expansion.
Pretty sure the newer Uboats have a connector plug and a battery switch behind the rear door with all the other switches. If you want to "MU" the Uboat to other locos be sure and look for the connector wire before you buy it. By the way the gearing in the Uboat power trucks is different that later produced locos so it runs faster that the newer locos when coupled to them. You can "MU" them to other Uboats, the FA-1s & FB-1s and the RS-3 because they all use the same power truck.
Aristocrafts Basic (Orange) unit will run up to 2.5 amps.
Only concerns would be this unit is not linear and use with sound units could be flaky.
For your question of a U25, no problem.
Only other issue with the Basic TE is itis not digital control, so any operation on the 27mhz band can affect its operation.
Case in point in my house is a Rokenbok 1/24 set being on would interfere and make the Basic TE not work. Solution was shut off the Rokenbok.