most of the filtration media are made of the same material, the only exception is the packaging which is designed to fit correctly into your filter's media compartment.
bio media serves a very specific purpose, which is to provide greater surface area for beneficial bacteria to colonize... that's it. so whatever brand that fits in your filter will do the job. i don't even use carbon anymore, since it has to be replaced and the costs can add up. it's not a necessary media unless you're trying to remove medication or other chemicals that you've added [accidentally] in your tank.
sand is actually an excellent substrate for messy fish, because sand is very compact, so there are very little crevices where uneaten food or other organic waste may settle. so what's on the surface of the sand can be easily removed manually or via filtration. gravel, on the other hand, is big and gets very dirty very quickly.
i'd suggest that you add another filter, since canister filters are exceptionally powerful when it comes to aerating your water, you probably won't have the need for a separate powerhead.
as for your fish dying, that could be a whole other discussion in itself. i have no idea why unless you give us more details on your water quality, parameter readings and what are your regular tank maintenance that you carry out.
