My advice, that some people experienced !
USE MODELS ONLY
Even the game Silas , use models only fro good frame rate , and the gams have no complicated levels !
With A8 supporting lightmaps, you can import from Blender (for
example) , your lightmaps , so you'll be able to have a good quality !
If you go that way you'll have a big boost on performance !
Another thing is LOD, i've used LOD in a sandbox game to test,
and it's really really easy to implement and allow a big improvment on frame rate !
For your game you could use it on characters/monsters;
and level assets using reltime shadows for example !
Just my personnal advice, now do as you want

!