Under armor comes in two variants, the flat alum panels, and then rock sliders along the edges. I have both, they are compatible with each other.
The Rasta4x4 armor comes in 4 pieces, I do not have the radiator guards, so I just have the three main segments. They work fantastic, and have heavy scarring to prove it. I recently pulled mine off and hammered them flat again
The rear most piece goes under the transfer case and can rub against the exhaust. This is bad, and rattles loudly. I used some spacers as shims on this one plate to keep about 1/4" clearance and life is good once again.
To complete your armor, take a good look at these rock sliders:
http://www.shop.offroving.com/product.sc?categoryId=3&productId=193 They are the best you can get, and are totally bomber.
The Rasta rear tire carrier is pretty good from what i've heard, though the latch can be fussy. I know one guy who modified the latch with a simple pullpin and he is much happier. The only thing I don't like is that the tire is mounted on the wrong side of the car. To me, I feel it should be mounted on the left side, to be more convienant when loading the car from the curb or wherever.
There are two other options for rear carriers:
1. 4x4intelligence in Australia makes a nice one. Here are shots on a DII, but my buddy Simon over there has one specific for the LR3 that is very similar.
http://www.4x4intelligence.com.au/rear_bar.htm
2. Kaymar makes a whole steel rear bumper. It's exactly the same as the stock bumper, but in heavy steel. It has tire carrier and jerry can carrier options, and you can spec the carrier type per side. US distributor is
Man-a-free on the west coast.
It's great to see your enthusiasm for the LR3. Straight from the showroom floor, it is the most capable off road vehicle Land Rover has ever made, bar none.