I have an older Optima Orange Top that is getting a little long in the tooth. It still does the job and I hesitate to replace it because it has a higher amp rating than the regular Optimas. But time marches on and I have been keeping an eye out for a replacement. The Sears Diehard Platinum is now a relabeled Odyssey selling for about 2/3 the price.
As far as an emergency power source I took a chance on a 24ah "emergency jump start" unit on sale at HF for $59. All I wanted was the battery inside (after pricing 24ah gell cells). I ended up using the battery, part of the housing and the electrical components. I did rewire everything with heavier wire except the jumper cables that were 4ga. It has a main power disco sw, volt meter, 12vdc/120vac charger, cig lighter socket, charge indicator, 2 charging cords 12v and 120v and it all fit nicely in one of those knock off surplus "tool bags". The battery will jump start or completely replace the truck battery in a pinch. I tested it by spooling 100' of winch line against a dragging emergency brake. The second pic is a matching bag with all the 12v air comp/tire repair stuff.