I tried Key Shot 4 within a trial period once. It is a very speedy pure CPU renderer for Mac OS X and Windows and you can export via OBJ to it and then set-up materials internally. As almost all external rendering engines, it takes quite some time to adjust the materials. I very much liked it and the speed is within a bit slower than Octane margins on a decently fast computer only, but unfortunately the price tag is rather high with $995 for the base version even, so I pretty much gave up hope for that one.

As was said before, Blender Cycles or LuxRender are probably the renderers that are cheapest to try out price wise. LuxRender is relatively easy to set-up and the automatic material translation of both DAZ Studio plugins (I used Reality in the beginning and then switched to Luxus) is at least good enough for many materials. Note that these two LuxRender plugins have a very different approach how e.g materials are handled respective adjusted. Luxus tries to integrate fully within the DAZ Studio surface tab and allows also for direct, textual LuxRender definitions passed to the renderer, while Reality uses a separate window for material setup and a material database that gets filled by users of Reality. I never tried out Cycles since me and Blender don't go along well