Heat pump 10 or 12 SEER

[Val]

We are interested in purchasing a 1902 SQ ft. Valley triple wide. We want to put a heat pump in it. The standard is a 3 to 3 1/2 ton 10 SEER, would a 12 SEER help decrease our electric bill more, and what about ton size? I know these are very well insulated and I believe the 3 ton is near it's limit at 1900 square ft. I had no idea an oversized heat pump could damage the home, so I want to be sure we do it right. Thanks