Magnepan, How Low Can You Go...power-wise

More power is better, but - If he powers them with the Sim amp in question he will be fine.
He'll get to Brazil, plop down on the couch with his favorite beverage and smile and be glad he bought the Maggies for a great price.
If he finds another ex-pat with 1000w monoblocks at a great price he should buy them as well. But the OP's question wasn't "What's better, 150w or 1000w to power Maggies?", which is where this thread has gone more or less.

btw: I've owned 12's and 1.6's for about 10 years, no longer have them.

Sebrof is correct. But the op also asks at some point if he would be doing a disservice to them with the simaudio. The answer to this in my opinion is yes.

Magnepans need enormous amounts of juice to sound their best. They can sound good with much less power and even nice with low power but if you want to hear what they can really do need big time power. I would say 600 a side at 4ohms and more is better.

It has nothing to do with loudness-

In my experience, 300 wpc was enough to play Lawrence Welk at moderate volumes. If you like Pink Floyd, Radiohead, Yes, Hendrix, The Who, Beatles, Nine Inch Nails or pretty much anything else that isn't chamber music, you should probably sell them and find another speaker.

Hi,
I own 1.6s. 150 watts is not even really enough for the 1.6s, let alone 3.6s.

It's not that they won't play or that they'll sound bad, but they won't really fully "blossom."

Maggies love power, and high-quality power. They're not that expensive, but require amplifiers that are powerful and often, expensive.

I just looked at the stereophile measurement panel of the Simaudio i-7.
It popped the 8 amp rear panel fuse at 320+ watts into 4 ohms.

That should do, no? especially since the OP seemed at least minimally content with his Nait at 50 watts. This is at least 6db increase.

Figure what? about 200 to 250 'real world' watts.