If the 5.4V makes a noticeable difference
you have either chosen the wrong motor or stepper driver
(on a good day 3mH less 20% = 2.4mH which is ideal with your 50V power supply )
how precise are you going to set the motor current ?
2100 ohm resistors are available from the E96 range
mouser.com
Mouser No:
660-MF1/4DCT52R2981D
if buying the resistors locally restricts you to the E12 range
1800 ohm & 390 ohm resistors in series will give you 2190 ohms
(with resistors in series you only have one wire to soldered to each of the 9 pin plug terminals)
John