You both got it mainly right, except for price and number built. Original price was $895,000, and there are 27 registered by the FAA in today's checkup--BUT, and this a big BUT, 4 of the 27 replicate earlier serial numbers with different registries so more likely there are/were 23 actual Adam A500s built and registered. This would not account for any destroyed/deregistered; if that ever happened. My answers follow.
1. Adam Aircraft.
2. Adam Aircraft A500.
3a. Two Continental. 3b. TSIO-550-E 350 Hp each.
4. $895,000 original sales price.
5. All carbon fiber construction.
A definitive illustrated 7 page article about the aircraft is in the AOPA PILOT issue of July 2003 showing flight photos, interior and full specifications, performance figures and limiting and recommended airspeeds.
Thank you for your quick responses.