Both EHEIM and Fluval are good brands. I lean toward EHEIM because I have first hand experience with this brand. It is a reputable German brand. Fluval is good too from what I have heard from other users.
Yeah, canister filter is the best choice for such large aquarium. It is really efficient and quiet.
My experience with EHEIM is limited to the classic series. The professional series should work great too since it is the same brand. All the reviews I have seen so far at online vendors turn out to be good just as I expected.
As for the fish, one little advice from my first hand experience. Do not put more than one gourami in the same tank. Most of the gourami species are aggressive toward each other. I have watched female Dwarf Gourami attack each other and only to be stopped when a male attacked them both... lol. So just one gourami per tank please.
I believe the fish died due to weak stock. Nowadays it is hard to find high quality fish from local fish stores. Losing a few of them out of a large batch is normal from my experience. When I ordered high quality fish from online vendor, I lost none out of dozens.
With a fish tank that big, I would get Discus. I know they are not cheap, but they are awesome. I also recommend German Blue Ram. Both will work in the same tank as Angelfish.
I just found a video with these fish in one aquarium. Check it out.
