I use Pano2VR, but since last using that I've also been teaching myself javascript, so I'd probably use that to build my own portal these days.
I understand Chaos have their own system now? I think?
I know there are a few others out there though but never used any, so no comment from me on anything else.
P.S. I'd take my 150% ballpark with a grain of salt - I don't think it's 150% amount of work compared to a regular still image. It's likely a lot more, but sometimes you can get away with less detail (especially in composition).