apparently fastturtle hasn't seen The Truth About Graphics Power Requirements v2
and here is a quote from an unrelated article
The power spec has also been increased. A new version of the power supply connector that is used for graphics cards that need more power than the slot can deliver (sometimes called a PEG connector, for PCI-Express Graphics) has been introduced, changing from 6 pins to 8. A single x16 card may now draw up to 300 W of power (75 W from the slot itself, 150 W from an 8-pin PEG connector, 75 W from a second PEG connector), up from 225 W (75 W from the slot, 75 W each from 2 6-pin PEG connectors) or originally 150 W (75 W from the slot, 75 W from a 6-pin PEG connector).
As you can see only 75W are pulled from the slot no matter the PCIe version.
The number of cards that exist without the extra power connectors is too long for me to bother trying to update a list.
The fastest of which from the gaming standpoint is the newly announced Go Green HD5750. It is however a 2 slot design (3 if you want to strap a fan to it or leave room for extra airflow)
The HD5670 is the fastest of the single slot cards that are energy efficient.
The lowest power modern card is the HD4450. The HD5450 will be out within a month and will probably be lower power than the 4450. There may even be a HD 5xxx that will be even lower power than all of the above cards sometime in 2010.