It sounds to me that your filter is working OK. My intake generally looks like yours or worse and the fact that your filter pads are always grungy suggests the pump is doing its job.
Having said that I don't know of any folks who regretted upgrading to a canister.
mine look the same way, its easy to just take it off and the filter does an awsome job. I also have a huge driftwood in my tank.....
every few days I clean ot off, easy and the filters do an awsome job. I am getting a emperior 400 today! I love the bio wheels and I make my own media sponges so I spent nothing really any more on filters