Yes, the Concert Lead would be fine to play bass through. The Concert Bass, at least the older style silver black was the same circuit as the lead. The lead didn't change all that much with the newer standard model.
If you're going to be playing your amp through only the 2-15", get the 8 ohm and wire it to the other in parallel to give a total of 4-ohms - which is perfect for both beta and concert amps.
If you're going to use an additional cabinet, then say so because using one 4 ohm and any other cabinet will drop the impedance below the 4 ohm limit of either beta or concert.
