The ASUS P3B-F is a version 1.0 AGP board.
AGP 2.0 cards (ie cards capable of AGP4X) are almost always fully compatible with AGP 1.0 motherboards.
The reason why some manufacturers state AGP 2.0 requirements is that some older AGP 1.0 motherboards, ie many 440LX boards, some early 440BX boards and most Super 7 boards, cannot supply enough power to the AGP card.
The P3B-F DOES supply enough power, so you should have no problems.