This is taken from the Hercules website under the system requirements for the 3D Prophet II:
Pentium® II / AMD K6® and higher or compatible
<b> Available AGP slot </b>
64MB RAM
10MB hard disk space (More to install games)
CD-ROM or DVD-ROM drive
Microsoft Windows® 95 OSR2, Windows 98 and higher
Says only "available AGP slot." Using only AGP 1x might slow things down for you, but then maybe not. I would also be more comfortable if Hercules had said 1x/2x/4x or something like that. It almost looks like they just forgot to specify it, which means 1x may or may not work. You could try emailing Hercules at cservice@guillemot.com or NVIDIA at info@nvidia.com to find out more specific information. Post it here if you find a clear answer as I have wondered about this myself.
Actually, as I get to thinking more, are you sure your motherboard only supports 1x? In fact, though I could be wrong about this, I think that any board that has an AGP slot supports 1x and 2x. Don't get confused by the specification: AGP 1.0 can do 1x/2x. AGP 2.0 can do 1x/2x/4x. Stupid, eh? Anyway maybe you should double-check that. I bet your board does 2x because 2x was included in the very first AGP spec.
Cheers,
Warden