Size 275/40-20, right?
General doesn't make any tires for your car.
The G-Max is available in the size, but the speed rating is W. The OE speed rating is Y, and most tire shops won't install a lower speed rating than what originally came with the car, except for winter tires with the mountain-and-snowflake symbol, where it's OK to sue lower-than-OE speed rating because there's less heat when it's cold and it's understood that speeds are lower in the snow.
Do you actually take this thing off-road or anything remotely near what a Range Rover is capable of? Or is it just used as a car?
If it's just used as a car, here are some good tires for you:
Nexen NFera SU1
Falken Azenis FK453CC
Hankook Ventus S1 Evo2
Kumho Ecsta PS91
Yokohama Advan Sport
If you want an all-season:
Continental DWS06
Yokohama Advan Sport AS
Pirelli Scorpion Zero Asimmetrico
Pirelli PZero AS
Remember that General is made by Continental, so if you like the G-Max, you might like the DWS06 as well. Both are UHP all-season tires.