I wouldnt recommend it since ATi says a minimum 500w PSU is required. From the official website: 500 Watt or greater power supply with two 75W 6-pin PCI Express® power connectors recommended.
Putting one on a 460w PSU would be a big risk. Get a bigger PSU and if possible, something better than a CM ExtremePower PSU
Yeah, a new non VR SP IP or a sequel would be best. They can't count to 3 so a sequel doesn't seem likely. Portal is my favourite and would love a sequel but don't expect one. I think I'll take whatever if they bring it on consoles too. Might go for VR as well.