Yeah the 80% efficiency is from pulling from the wall to the components, the 20%+ is lost to mostly heat.
Some PSU manufacturers rate their PSU based on peak output, but some also put it as the lowest constant they can output. Most seasonics and corsairs can put out a lot more than their label for short periods of time.
I installed it as well, but just the animations and loading inbetween races and series is just annoying. Even if I had a laptop on the couch sitting next to me, I would have to concentrate to keep hitting buttons to navigate the menus and all that. I enjoyed the experience, but I think it'd wear off pretty soon anyway.
GT5 was good, but I spent about 90% of the time in the menus rather than racing. My time is better spent on iRacing on the PC where I can browse forums and multitask while waiting for a race to start, rather than sitting there bashing my face in during loading screens and backing out and having to search for a car that fits the criteria after I realize I don't own the right car for the event I want to participate in. Or somehow getting 800,000 credits after 40 minutes of actual racing.