I'd say yes, it's totally worth it.  I've had gaming rigs, so I've always had pretty good video cards.  Poser's rendering has ALWAYS bugged me.  It certainly has IDL flaws.  BagginsBill is a wizard, and can eek very good results out of it but I am only a padawan, not a Jedi master.  I pretty much gave up on scenes (enclosed spaces), Poser's implementation of lighting would drive me nuts trying to sort things out. I've used BB's environment sphere and light meter too.

I've found Octane to be far easier in terms of the lighting to the hobbyist.  Place lights as you would in the real world, and it behaves pretty like you'd expect it.  I never got that in Poser.  All these tricks of IBLs and 50 lights trying to illuminate a scene.  I've tried Luxrender as well, and even with 3.8 GHz i7 it was just too slow for me.  For reference, I have two EVGA GTX 970 cards.  I think the pic linked took 5 or 6 hours.

Having to edit textures in Octane is a pain in the ass and the drawback, but the results I believe are worth it.

Warning!  Link has nudity.  Not my best, but here's one I re-visited in Octane.  Similar lighting.  Link to Poser version in description.

http://gator762.deviantart.com/art/Charmane-Play-Redux-523296678