Did we really need 3 threads on the same amplifier in the same hour by the same person...?
The IPS-1 and MPS-1 are modular designs, meaning they're essentially 7 monoblocks in a chassis. They'll have better channel separation because the channels barely, if at all, interact with each other. On that note however that era of Emotiva amps had their power ratings given at 1% THD, while the more recent ones IE the UPA-7 power ratings are .1% THD, so you can probably bump the IPS-1 down to ~140wpc instead of 150 wpc, which is pretty much identical to the UPA-7 in 2 channel mode (140wpc) although less in ACD mode (~120wpc) which for what it's worth it negligible.
What the UPA-7 had as its advantage is that it uses a very large power supply, meaning it likely has more capabiliity for instantaneous power draw for any given channel.
XPA vs UPA
From what I've heard, and I don't know if I believe it the UPA series is a bit more tonally neutral, while the XPA-5, 3, and 2 are a bit more energetic up top, and the XPA-1 returns to the UPA sound with extreme power.