If the input of your exciter is unbalanced, it is probably on the order of 10k ohms+ and will likely accept anything you want to feed it with, levels notwithstanding. If it is in the same rack with the source (computer, STL, Barix, mixer, etc), balanced or unbalanced will probably not matter. Professionals prefer balanced lines, but that matters mostly when you are trying to be consistent, are mixing equipment types or have low level lines of some length.
If you feed your exciter with the 600 ohm output of some amplifier, processor or STL, it is possible THAT component might want to see a 600 ohm load, which your exciter might not provide. In that case, you might need to put a resistor across the output, if the performance doesn't seem right.
A side note: if you're going the other way... like having a high impedance source (consumer grade cd player, etc) feeding a 600 ohm "something", the source equipment may not generate enough level to drive the low-impedance input of the next component. You'll need a matchbox of some kind to interface between those parts. That's more unusual though. If you're not trying to hook up an old broadcast console or analog audio processor, you might not ever run into this problem.