In this picture you can see a Footsore Miniatures Barons Wars knight (holding his helmet), Crusader Miniatures Knights, Gripping beast knights and 1st Corps/Curteys foot soldiers.
Gripping Beast, 1st Corps and a Crusader knight with a Fireforge raised arm and axe.
This Crusader Miniatures mounted knight also has a Fireforge arm and axe
In this pic my knights by all of the above manufacturers are engaged in a melee with Captain Bloods Fireforge plastics:
And here my mounted knights do battle with Captain Blood's Firefore knights.
So in summary:
Crusader Miniatures
Gripping Beast Miniatures
Footsore Miniatures Barons Wars
1st Corps/Curteys
They all blend in together and will work alongside your Fireforge figures.