Well, I don't think you'll get anything better for $25. Also, check if they have more than one in stock, as they don't mention that on the website..
What kind of audio editing are you planning on doing? If you want to work on lengthy sections of high quality audio, I wouldn't even be looking at Amigas to do that type of work. If you're preparing samples for music, then the processing power is fine, and you can get away with less RAM.
For some applications, you can quite happily break long sections of audio into sub-sections for editing, allowing them to be handled more easily with limited RAM and processing power. However, this can be extremely inconvenient in some cases. When I mastered a language tuition disk, I broke it down this way, for most of the editing. Saves time overall. I would not do this for final mix processing of a musical track, though.
How much RAM is enough really, depends on what kind of audio you are doing, and what sort of editing. Some elaborate effects processing can also take a bit of RAM buffering.
Anyway, if you buy the card and regret it, you would most likely be able to more than make your money back on ebay.
