AFAIK, Eyefinity works with three displays connected to a SINGLE card.
Unlike NVIDIA, where you can connect three displays on any of the four display connections-hence an SLI requirement.
Also, one of the displays must be connected via DP/DP adapter (active).
You can eliminate the DP problems with a DP>VGA adapter, however, this is an analog signal with a max supported res of 1920x1080.
I understand your problems with DP adapters. TBH, I think they are shite.
I have had ENDLESS problems with these.
I have tried:
1. 2 Accell B087B-002B and Accell B087B-002J FW 0.43 and 2.0. Total cost: $500 (including shipping os),
2. BIOS flash,
3. USB wall adapter (5V, 1000mA).
Any driver after Cat 10.3 seems to make the problem worse.