GLScene should be good but it's Windows only AFAIK (maybe i'm wrong?).
You are it works in Delphi, Kylix and is being ported to Lazarus.
Go, go GLScene !!!
I hate D3D but fortunately it's used by all DX games.
SDL is BIG allright, too big, look at GLFW, now that's a lib for my taste.
What about SDL calls, can i call OpenGL functions or do i have to call SDL ones.
I also hate VCL games i used VCL for terrain editing but hacked the TPanel message proc for a speed boost, because i was lazy to write a whole 3D GUI.
The fastest demos i've seen are those on Sulaco and the ones from FPC wich run extremly fast on Linux, i only need a lib for window management, the rest can be done with Pascal code(i wish everything could be done in Pascal code).
I could use the API on win but i don't know much about X calls/signals, if i knew that i could write my own crossplatform unit for window management.

Thank you guys !