I'm thinking about roll stiffness and how the car would handle. You don't want the rear to be stiffer than the front in roll or the car will have major oversteer and wag it's tail around corners.
If money is limited I'd buy parts in this order to insure safe handling.
Option 1
1. Front anti-roll bar
2. Rear anti-roll bar
3. Front springs
4. Rear springs
Option 2
1. Front anti-roll bar
2. Rear springs
3. Front springs
4. Rear anti-roll bar
You can do option 2, items 1 and 2 first, then add the front springs or rear bar separately later.
Do not drive the car with front stock and just rear springs and bar added, you will have oversteer. The rear bar can be added any time with no problems.
I like the Adco rear bar end link attachment points better, it attches to the frame rails in the rear, the Hotchkis bar attaches to the center of the rear seat kickup with 4 bolts on each side.
I don't know for sure if the Hotchkis and Addco bars are the same effective rate. I think they are pretty close, but I don't have the exact measurements to compare them. You are far better off using the whole package from one manufacturer.
We installed the whole TVS system on my wife's 73 Camaro and it's almost perfectly balanced.