The Toyo Open Country A/T II is a good tire. The Nitto Terra Grappler is the same, structurally, with a different tread. Toyo owns Nitto. Personally, I prefer the Nittos. There are better A/T tires on the market, including the Falken WildPeak A/T AT3W, the Michelin LTX A/T2, the Continental TerrainContact A/T, and the Goodyear Wrangler TrailRunner A/T.
Now, that said, JayArras does bring up a good point. The question is, "Does where and how you drive your vehicle warrant all-terrain tires?" Unless you do a lot of off-road driving in your R52, all-terrain tires aren't the best choice. If you drive on most highways, paved roads and maybe even an occasional, light off-roading, you will probably be better off with All-season, Crossover/SUV tires, like the Kumho Crugen Premium, the Hankook Dynapro HP2 or Toyot Open Country Q/T....or even a All-season truck tire, like the Continental Cross Contact LX20 Ecoplus, the Michelin Defender LTX M/S, the Firestone Destination LE 2, Kumho Crugen HT51 or Hankook Dynapro HT, the latter two I have on my 06 and 08 Pathfinder and am very happy with both.
Tirerack.com has a tire decision calculator at their site which might help you decide what type of tires would be best for your needs. If you put A/T tires on your R52 and do mostly highway driving, you may not like the ride quality of the vehicle afterwards as much.