Wow. . . That's . . . Crappy. I have HOB filters that I change the media once every two or three months. Up until just a few days ago I had 5 juvenile axolotls in a 20 gallon tank (read as: WAY overstocked) with a Marineland 150 on it and I didn't even RINSE the cartridges but once every two or three months, let alone change them. I think since I put the axolotls in that tank in February I've only changed one cartridge, maybe two. How often & how much water are you changing in the aquarium?
If you really have that much debris in the tank, a canister isn't going to be extremely effective. More effective than a HOB, yes, but not extremely effective. Canisters really shine with biological filtration, and debris in the canister clogs the media where bacteria would grow. It also results in nitrates and such growing really fast.
Were I in your shoes I'd probably put on an Eheim 2217- I have one of those on my 60 gallon and LOVE it. It pumps a ton of water and doesn't slow down even when it hasn't been cleaned for months. But, I'd put a prefilter on it to help cut down on some debris in the canister. You can take a large chunk of sponge (like for an AquaClear filter) and put it over the filter intake, and that would prevent tons of stuff from getting sucked in there. Then you can take the sponge off once a week or whatever, rinse it off, and put it back on. Kensfish.com has 2217s really cheap- actually cheaper than a Cascade 1500.
That, or I'd put a prefilter attachment on a powerhead and see if I couldn't cut down on some debris in the tank that way. And I'd do a bunch of water changes. IMO, water changes are a better way to clean the tank than even the best filter.