I've fitted a DTUK tuning box. I know it's a bit iffy as to how much power is added as all cars are different. I guess many will say it isn't as good as a full re-map, but I'm not wanting pay many hundreds of pounds to have it set up on a rolling road. The box certainly has made a difference,it is easy to feel, and hasn't blown up yet !!
I liked my Disco, did nearly 100k miles in it, I feel the GC is a more comfortable place to sit, more toys as standard, handles better on the road as suspension is firmer, but on the flip side the Disco air suspension is better off road as absorbing bumps and holes, it just seems to react quicker rather than GC. Always loved the 8 speed ZF auto in the Disco,that helped my choice of getting a GC