Can't help about how the bidet seat looks on the Legato. Plainly it won't look as integrated as, say, something like the G500, Model No. MS970CEMFG, which is only gonna be, say, $200-300 more than the sum of the price of the Legato and your S300e Washlet, depending upon where you buy it. It's a Washlet with an integrated toilet. (It's not a Neorest; it's available at a significantly-lower price point than the Neorest.) Just a thought.
Here's the spec sheet on the G500. Note that it does have the double-cyclone, the dual-flush, the universal height, and Sanagloss, kind of like the Maris did. And the G500 will say "Hello" by raising its seat for you when you walk near it to use it. Here's the spec sheet: http://www.totousa.com/Portals/0/Pro...MS970CEMFG.pdf
Note -- very important -- that unlike most Toto toilets, which have at least 3/4" clearance between the toilet and the wall and so will fit if the centerline of your toilet flange is located a little less than the full 12" from the wall, the G500 requires the full 12", and basically is going to be right against the finished wall.
As to the Aquia, it's a great toilet that almost all of its purchasers love. The Legato doesn't have a lot of ink on any of the forums or review sites that I have seen, but there's no reason to believe that it won't flush well, like any of the Toto toilets (other than the sub-$200 "builder-grade" ones with the 2" flush valves that Terry doesn't even sell).