The only Sterling model that was sold was the 800 series, which was a rebadged Rover 800-series but with different specifications tailored for the American market.
The 2.5 L Honda V6 was a completely different engine from the Rover KV6 engine introduced in 1996 (only sold in the U.S. in the Land Rover Freelander), although the two share the same 2.5 L capacity and V6 architecture.