I would definitely bump up to a larger tank. Frankly, I'd go with a 2' x 2' tank, as 1 MH can light that well ... why waste the light that would escape a smaller tank?
Nevermind more water volume just makes the whole thing easier [a skimmer for this tank could handle a little larger IMO, flow the same].
I would think getting good flow, but not direct flow, in that small a tank would be difficult. For slower-flow-liking corals we had good luck with a nano ... but I know I wish for a far larger water volume on my 58 for my Acropora. IMO, smaller tanks [given fluctuations] don't have to, but tend to grow a little slower than larger water volumes. To take very slow corals, put them in a slow-growing environment ... might not be a lot of `payoff' IMO.
Personally, I'd be sure you have luck with SPS in such a small tank, and seeing how growth/color is before spending for some of the most expensive frags `out there'. Maybe it's me, but I don't have any of those [except a pink millie] and beyond the unusual birdsnest ... have found corals that I find just as pretty, maybe more so.
But if your nano just turns Acropora brown ... would be some mighty expensive tan Acropora there.