The tables on wikia are pretty good for the rings and amulets:
http://regnum.wikia.com/wiki/Rings
http://regnum.wikia.com/wiki/Amulets
For rings, Ignis has Rol with +5% attack speed, so two = 10%
Syrtis has Deadly Sight, 15-25 damage, two = 30-50 extra damage per hit (average 40)
Alsius has Blacksmith, 9-15 damage, two = 18-30 (average 24)
If your (Ignis) weapon averages more than 400 damage, two RoLs are better than two Syrtis rings; if it averages less than 400, they Syrtis rings are better.
Compared to Alsius rings, if your weapon does > 240 damage, you're better off with two RoL than two RoBs.
Amulets: Both Syrtis and Alsius have the Royal Amulet (100 HP, 45 Mana).
Both Ignis and Alsius have the Emanation amulet, (100 Mana).
(Does Alsius really have Emanation? I don't remember that one, and I'd probably use it over the Royal.)