Wrong section, hopefully a mod will move this :p
Anyways, 4.60 is downgradable depending on your PS3 model, though I don't believe official tools for that firmware is out yet. I'd probably wait a while for them to release and become stable before doing anything major. As for firmware, I use PS3ITA 4.50. It's a full DEX which means updates aren't necessarily required to play online, and since it's DEX it's easy to RTM, as you said. It will also work with CEX tools if you install CCAPI on your system.
There are plenty of methods on how to downgrade and go to 4.50 ITA, so I'd just go with one that seems to work for you. I'd recommend sticking with one tutorial rather than a few though, to lower the chance of PS3 bricks.