I just got to the house and looked up the link to the site I have been checking for a Dolphin pump for the 90 gal. They have the 5100s listed with a bit more info.
Dolphin 5100S AMP Master S-Series Pump - SeaQuestMarine.com
After looking over the graph a bit more closely, it may not be a good choice due to the low head pressure rating of that pump. 2400gph at 6ft. kinda stinks for a 300 gallon tank. As I have been looking over pumps for the 90, I am aiming to have enough head pressure to use mutiple, adjustable return heads for tank circulation and eliminate all powerheads from the tank. I am aiming to have one pump do everything that needs to be done.