If you have Poser Pro you can use Poser Fusion to host a static Poser scene in Maya. A single lcense of Arnold will cost $1300 (educational licenses are only sold to institutions), and right now there is a 5 license minimum purchase (though they do say this restriction will be removed in the future).

But if you have Maya, Maxwell render would probably do a great job for you, It's built for a production environment, is fast, and used in many different industries, where Arnold is really designed for use in larger VFX/CGI houses. Maxwell is only $795 per seat.

If you take a look at the features comming out in Octane 2 they are pretty impressive. But 1.5 does extremely well. So for just a little more than the price of a single seat of Arnold, you could get Octane, the Poser or DS plugin, and a Nvidia Titan to run it, and you could have jaw dropping renders in seconds to minutes (with SSS, caustics, etc.) all with live updates everytime you change something in the scene. Using Poser Fusion, any pose/prop adjustments need to be done in Poser, saved, then reopened in Maya. Also all matereials/shaders and lights will need to be adjusted/setup in Maya.

With DS, you would need to export the scene to Maya as .obj, then open in Maya, setup your mats/shaders, and render. You could do this same process using Blender/Cycles for free with mcjTeleblender2.

Keep in mind that in the hands of an accomplished artist (i.e. someone who knows the shader/lighting system inside -out), just about any modern render engine is capable of outstanding results. The one area where FireFly falls on it's face is cuastics (not available), 3Delight supports all the major features and is very stable. I've never used Arnold, and probably very few, if anyone, here has, so I can't say how easy it is to use. But before jumping into a $1000+ render engine, I'd definitely explore the other options first, but you milage may vary 

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