If it is 20W for 1000 Lumen then it is 50 lumen per watt - about the same as fluorescent lamps (50-100lm/W).
The first link shows one type, limited data found, but note the comments on heat-sink issues.
The second link is a data sheet, showing one type that needs 12-15V @up to 1.4A. The biggest issue is temperature. Surprisingly there is no thermal resistance spec. However the Tjmax (max junction temperature) is 120C, so allowing that we don't want it that high, if the ambient is 50C and the Tj is 100C, that means 50C rise is allowable, and that means an overall thermal resistance of 1 degree C/W, including whatever the junction to case is. A heat-sink with 1C/W on its own is a large multi-finned thing about 150 x 150 x 50mm, so this LED needs something like that with a fan, to run at full power. The connecting leads are apparently also the heat-sink (thermal) connections, so you will need to devise a way of splitting and insulating the heat-sink, so the electrical connections can be made while the heat is also conducted away. The heat-sink will be close to boiling water without a fan, so no bits of plastic around. A fan is essential, unless the power (current) is less than the full power..
The driver circuit:
This will be a constant current supply that provides > 14V DC on no load, with the current limited and controlled to 1.4A or less, preferably adjustable. The voltage will pull down to the LED voltage when connected. It is definitely not a transformer, or the normal wall adaptor that produces a constant voltage. It will need a special device. I did find some Omron units (Farnell) but they were > $100 and rated for 24V so not sure they would even be suitable. However this is an indication of the price.
It would be possible to use a constant voltage 24V x 2A (using up to 1.4A) supply with a series resistor as the ballast. This resistor would be calculated using ohms law as (24V-12.8V) / 1.4A = 8 ohms so an 8.2 ohm power resistor using standard value. The power rating of the resistor would be V x I so about 16W. At least a 25W resistor size is needed so it won't get too hot. This method is wasteful, but it will work so you can see how hot it all gets. An old DC type power supply for a lap-top might suit this if the resistor is recalculated for the actual voiltages (could be 18V)
A true supply for this needs to be a switch mode regulator using an inductive ballast, running from 24V (derived from a wall outlet) and designed as a current regulator.