From what I can tell, Alphasim's offering has about as much functionality as Antti's original for 2002/2004.
That is to say that it is a solid model, but I would personally not consider it a "systems simulation". Note that I do not own Alphasim's offering due to being exceptionally happy with some variants that I operate in FS2004.
With the above in mind, their AS365N is the only FSX compatible Dauphin/Dolphin you're going to find right now, so it all depends on whether or not you really need a 365 for FSX at this time.
Regarding the EC-155, you may want to ask in the forums at
www.hovercontrol.com.
I remember someone there was working on one, but I have not heard anything from them in quite a while on it.