I have a 2009 NZ Carnival which is the same shape and I like both the Radian and Frontier installs in my car. My car has only done 32km so far and I can only tell you what it's cost me so far in NZ $$ but the last 30km service was just under NZ$500.
I personally like the install of the Frontier in harness mode (recline block forward) better in the rear row than middle - if we were allowed to install it in harness mode with the recline block back, I might like it better in the middle row captain chairs but I can only but dream on that one.
The only position I don't love the Radian is rf'ing in the middle captain chair of the middle row because I find it over reclines slightly as the two front seats are too wide for it to brace against. This probably only matters to me because I don't have babies and we now need a more upright installation. I've had no trouble getting quite an upright rf'ing install in both middle and rear row seats and it installs easily forward facing.
I took some photos for a NZ lady over the weekend showing some seats I have here and with the Radian rf'ing behind the driver. A wedge would definitely help even more but I've figured out a few tricks in the meantime.
https://www.facebook.com/media/set/?set=a.227936193938195.58157.140802319318250&type=3 (sorry about the funny link - let me know if that doesn't work)