The SEBO Felix should work fine for your situation, so I am not sure what is wrong.

It sounds like all you have are floors, so use the parquet floor attachment on the floor. This will pick up the litter, fur, etc. much better than the powerhead. If there is litter dust left behind, you might want to make a quick swipe of the area with a dust mop or "swiffer" type mop.

You might want to invest in a covered litter box. Another suggestion would be to put something around the litter box like a rug, so the litter stays put. Cats will also have to walk on it as the exit the box. All you have to do it remove the rugs and shake them outside.

If you do have allergies, I would suggest that you do vacuum your furniture regularly(at least once a week). The only time you would not is if you have hard furniture or something like leather, vinyl, etc. Go ahead and vacuum your mattress also. When you remove your sheets, to wash, just vacuum your mattress. A once a month mattress vacuuming should be fine.

Another suggestion could be to keep a soft broom and dust pan in the litter box area and sweep everyday. Or, purchase a stick vac for the area and do a quick area vacuum daily.

Let's face it, having pets requires more work. They also bring great joy.

There really is no need to purchase another vacuum, to replace your Felix. It should do the job really well.