Understood, but again, an old concern and not applicable anymore. To demonstrate, try to find a new ATX PSU that is 450W (what NVidia recommends for the 660ti) that does not have 24 amps available on the 12v rail(s) - you just can't anymore (unless you can find a new ATX V.1 model somewhere maybe). That is why I say it's not applicable info anymore. The connections are where the lessor PSU's will come up short, not the amps, in fact when I first looked up the PSU (I also check amps but I think that's just habit), I looked to make sure he had the PCIe connections available.
Define "new". Do you mean a new design or that the PSU has never been used?
The Corsair Enthusiast Series VX550 (CMPSU-550VX) isn't new. It's from 2007 and has been discontinued. It was great for a power supply unit from that time period.
If you're talking about new as in never used then you can still buy a crap brand RAIDMAX RX-450K 450W ATX12V Power Supply
that only has a +12 Volt continuous current rating of 21 Amps.