Alas, the ones from Direct Circuit are sized for the 987, second gen boxster, and I have the 986.... sending them back.
Althoguh the way you install it is via connection to the grill, not the dash, here is a photo showing it against the dash opening of our 2000 S, which gives you a sense of the size.
When attached to the grill, even without a speaker attached to it, it is not possible to fiddle it into place since the ring is simply too large with its substantial lip to fit on a first gen dash.
Looks like I'll need to pony up for the JMG solution, which is $50 instead of $20 -- but is sized more conservatively so it fits in a 986.