Only problem with Sonnet it... you can't buy it anywhere
Yes you have to find it second hand now. Sonnet sold off all the stock a few years ago at dirt cheap prices. They do periodically show up on eBay. And maybe at computer stores that sell used Macs.
I was lucky enough to get my Sonnet during the fire-sale. I paid $29.95 USD for the G3/500MHz version.
Elbox is shipping my new Mediator 3V 4000Di today so hopefully I will have it in a week or two and I can also actually use my Sonnet now