The RP155 is a much newer design than thr 2496 so I would doubt there is much difference in the converter quality. You have to get waaaaay above these price point for it to be noticeable and then only on the finest of source material and monitors. Operation at 96kH will do nothing for sound quality.
The MIDI....Yes! Pondered this for the mixer, must be able to control FX from a PC using MIDI I think. Jeeez! Hope you don't have any other plans for 2015, you are going to be busy!