The problem with the ARB bumper on the DiscoII is that it mounts to the crush cans(airbag compliant model), the crush cans are aluminum and will get crushed/bend when using the front recover points or winching. Subsequently the bumper will bend into your fenders and your head and your light (ask me how I know).
To get the most out of your truck do the following.
1) Most important, drive it stock. Learn how to negotiate the trails. If you can drive well and know your rig and its limits you dont need a lot else. Disco2s are immensely capable.
2) Look to see if you have CDL enabled. If not then look to see if you have the CDL nipple.
2a) If CDL nipple but no way to select, then buy a shifter or make a $10 shifter like mine
3) Good Tires. Depending on your terrain A/T or M/T. Trim your front bumper, remove the lower air dam first, this will help a lot on rubbing with larger tires and greatly improve approach angle. Also get a good recovery kit (I have 4 shackles, 1 snatch block, 1 tree saver, 1 snatch strap, gloves, winch hook, 25 ft of Grade 8 5/8" high vis chain, 6ft bridle strap, etc) also get a tire patch kit. If you need buy a come along or a hi-lift with winching accessories.
4/5 Dependant on terrain) Protection(rock sliders, diff guards)
4/5 Dependant on terrain) Suspension, 2" Spring/ shock combo medium duty or heavy duty depending on how much trail riding vs DD you use it for. Dont get spacers, do it right the first time. OME or RTE or L8. Stick with 2"
6) Bumpers, front and rear. Only benefit of front bumper after trimming is that you get recovery points and option of winch. Your rear bumper will need to be replaced way before your front if you trim your front. The departure angle is the weak point in terms of bumpers.
If you follow this list and spend the time learning your rig, by the time you get to point 5 you will tackle harder terrain than 95% of the people with more built up trucks. Too many people throw money at their rigs without really learning its capability first.
All of the above presumed you have done the basic maintenance first(U-joints, fluids, coolant system alteration, etc).
Let me know if you have any other questions.
-Sam