Yes, that is what mulm is and you don't need a lot of it. You should add it to your new canister filter because that is where the bacteria will colonize. Obviously, you don't want to put two heaping fistfuls of crud in your canister because that will just clog it up. Really, you only need to add a small amount. You want just enough to carry over a viable source of nitrifying bacteria from a healthy, established aquarium. It will multiply on it's own.
When Tom said to add enough plants from the start it was a very important statement. Do not put a few plants in and wait for them to grow out. This is very important to remember, I've dealt with this problem myself. Ideally, you would pack the aquarium with fast growing plants from day 1 and leave them for at least a week or two. You need these plants to suck up nutrients and out-compete algae so that you do not have algae or green water blooms.
I have used a HOTB power filter and could not stand the noise it made or how often I had to top off the water in the aquarium to try to keep the waterfall effect to a minimum. I purchased an Eheim 2026. It is the only canister filter I have ever tried. I am extremely happy with it. My aquarium is in my bedroom and I HATE inconsistent noises or humming. The Eheim is very quiet. I thought I heard it once, but it turned out it was the air coming out of my floor vent. I thought I heard it another time, but it turned out to be the lights in my room. That's right, when I flip on my light switch, I can hear that, but I cannot hear the Eheim that sits 3 feet from my bed. As far as how it compares to other brands of canister filters, I cannot comment as I have no experience with other brands.
As far as CO2 reactors go, I've tried a few methods.
First, I ran a CO2 line into a venturi nipple on a small submersed water pump. This pump shot the bubbles out in a very fine mist -- highly inefficient and the misting created an audible noise every few seconds.
Then, I ran the CO2 line into the intake strainer of my canister filter. This seemed to work well when using low amounts of CO2, but I did not like the idea of those bubbles slamming into my impeller at high speeds.
Next, I ran my line down into a CO2 bell made from a small softdrink bottle. This worked ok, but could not keep up even with yeast produced CO2, let alone compressed. It was also an eyesore and delicate as far as tipping over or cleaning around.
I then tried making my own internal reactor from an old siphon end and a water pump. This worked ok, but was also an eyesore and hard to keep submerged in a vertical position. Also, it did not keep up with the CO2 as well either, but it was the best method I had tried up to that point.
Finally, I bought an AM 1000 external reactor and ran it in-line with my canister. I put it off till the last resort because it was expensive. However, it works very well and I love it to death. Now, I can't imagine diffusing CO2 any other way. It is expensive for the material you get, but I think it is fairly priced when you factor in the efficiency and the convenience of it, let alone the improvement it makes in the appearance of your aquarium having removed the reactor to the outside of the tank. You can make your own external CO2 reactor, but that wasn't my idea of a fun project and knowing myself, I would have likely gone through several designs and ended up spending the same amount of money as the AM 1000, along with spilling several gallons of water in the process
I think setting up a freshwater planted aquarium is an easy endevour, once you've accumulated all the right equipment and have gone through the process of doing everything the wrong way at least twice in your past. If, despite your best intentions, you do end up with green water that does not go away easily, I cannot say enough nice things about the Turbo Twist UV Sterilizer. The fact that they can sell aquariums without these things is almost criminal. To think of the months I spent trying to get rid of green water when all along all I needed was a 9w turbo twist, a small pump, and three days. Like I said, do it the wrong way at least twice and you'll get a much clearer picture of what works and why.