JimC,
I don't think the DivX encoder currently supports any hardware. I read recently that a company (the name escapes me)will have digitizing cards on the market soon. I assume that with the software you can convert any format to DivX, but you may loose quality in the process(not sure).
As for Macs, they support DV video (firewire interface). Videos shot in that format rival Betacam SP in quality (DV actually has a higher luminance bandwidth), and can be transferred to a hard drive without compressing the source. Once in the hard drive, DV footage should convert nicely to DivX IMO. From what I understand, DivX is a perceptual video encoder (the video equivalent of EPAC)which means that the encoder only omits what the eye cannot see.