I hate mixing PSU's I would see how others with this kit are doing it with 120.  But each board is going to use more then the 400.  So I don't think 1 of the PSU's will run two.  If it was on the 220/240 with 1000 watts it would run two.  But your giving them to few of watt's I think on 2.  Unless they are underclocked then you could depending on settings. Also I'm assuming it's a batch 8 or 9 in this.

So ask seller if they do a mix of how they do on 120.  I would sit it aside till you get that anwser from seller or someone on here who has used it.