Large landscape terrain dropping fps alot? How can I get better performance?

When I’m making a somewhat large terrain, 500x500 I notice my fps goes from 110 (with no terrain just a small box floor and sky) down to 70-80’s when I add the terrain.

I don’t have the terrain selected, I tried different settings, Happens even without a material

My specs are decent radeon 7970 i7 3770k

Is it normal for terrain to drop fps by this much?
I’m working on a large scale open world project and I need a large terrain that still retains good detail for heightmaps and worldmachine goodness,

Or is it time to upgrade to a gtx 980? Is this normal? Unless there are additional settings to still get big & high resolution landscape/terrain but increase fps?