So, no advantage in using the XLR connection versus RCA ....To further confirm this, as can be seen in the schematic on page 12 (pdf page 14) of the manual for the D240 MkII the center pin of the "normal" RCA input connector for each channel is wired directly to the non-inverted signal pin (pin 2) of the XLR connector for the corresponding channel, and the "inverted" RCA input connector is wired directly to the inverted signal pin (pin 3) of the XLR connector. So you would be using the same input circuitry in the amp, and in the same manner, regardless of whether you used an RCA-to-RCA cable or an RCA-to-XLR cable. Also, although it may not be important, with an RCA-to-XLR cable you would lose the ability to readily change between normal and inverted polarity.
BTW, when (and only when) using RCA-to-RCA cables be sure to follow the instructions in the manual about inserting shorting plugs into the unused RCA connectors. (Or, alternatively, connect a jumper between XLR pin 1 and either XLR pin 2 or XLR pin 3 depending on which of those pins is wired to the RCA connector that is NOT being used). Noise performance is likely to suffer if that is not done.
Regards,
-- Al