I can vouch for slydar's comments on that deka, i used to work in a batteryworld shop and we used 2 sell those deka's for harley's and the like. They are an awesome battery and heaps small.
Another few brands i would look into are federal and optima.
Optima are wicked batteries, the 1 that they sold that is similar in size to a commonwhore battery is rated at 750cca's and i never tested one below 1000cca's pretty dear tho.
Federal make a battery that is an awesome size with 500+cca's, its called a 5MU1R i think, they are designed to fit in the back of MX5's (they have a boot mounted battery standard) and whilst they arent a fully sealed unit they are vented. They cant spill or leak acid at all and have 2 little vent ports at the top that u can run some plastic tube off and run thru the floor by drilling a 6mm hole (ish). they are pretty small aswell, the same size as a late model corolla battery only 2 inches shorter (NS40 size but 2" shorter).
Johnny rochester: those jumpstart batteries and computer backup batteries that you are talking about will run a car, but thats about it, they have a habit of frying the terminals inside the battery as they arent designed to cope with the load of a car electrical system, we had a few die a painfully death that way. Also, those oddysee batteries, they USED to be good, when i was in the industry they had a management change and turned 2 shit in the quality department, completely discharging in storage, snapping off terminals inside the battery etc and they had the worst warranty system ever. They would make you send the battery back to the states for testing before they would honour warranty. They also dont cope with current draw real well, they are a race battery so if u have anything electrical in your car more than engine runnings, a heater and lights they dont last long.
After saying that tho, if you really really want an oddysee, dont get an oddysee, get hawker energy industrial cells. They are what the black plastic cell is inside the pretty orange oddysee box only half the price, easier to get and better quality.