Chipsets for external enclosures are a difficuilt thread in my opinion. For example my DVD burner collection is more or less in external enclosures with USB+FW or USB only. The USB+FW combos use Prolific3507 or GLE811/OX911.
At all both combo chipsets work with no problem. Sometimes the Prolific is a little bitchy with some of my Plextor drives. I guess it is difficuild to recommend a special chipset. But from what I read the Oxford Semiconductor products are really good (under Windows).
In the contect of your question the term “bridgeboard” is a description of a PCB with a USB/Firewire/eSATA to IDE/SATA converter. In general a bridgeboard is more or less a protocoll converter from one bus (protocoll) to an other.
And one last sentence to your plan using ATA100 HDDs … ATA HDD drives are mor and more vanishing from the market and I’m sure in the very near future you’ll not find any new designed IDE HDDs anymore. I’d invest in a hardware using/supporting SATA HDDs… for this reason I’ll pimp a few of my external enclosures with an SATA comatible bnridge board supporting SATA optical drives.