Hello and thank you for your inquiry and being a Marine Depot customer.
I personally prefer to stick with the same brand of bulb over the tank. The reason being is that every manufacturers bulb doesn't always have the same color even if the Kelvin ratings are the same. So if you were to run a 20K Blue Life bulb on one side and a 20K Aqualine bulb on the other side you might find one side is more blue while the other side is more white. Some people like this look, I personally try to keep the same color over the entire tank. But there would be no harm running different brands, like I mentioned you may just find one side is different colored than the other side.
I personally prefer to use two part Calcium/Alkalinity products to supply calcium to my reef tank (unless I use a calcium reactor). These help to keep both the calcium and alkalinity where they need to be. The Caribsea Purple Up is a very good product though and I don't think you would have any issues using that instead of the powder calcium additive.
If there is anything else we can do for you please let us know.
Marine Depot Customer Service