When I needed to replace the Pets at Home Fullers Earth, I tried some Bob Martin Ultimate Odour Control litter, which is another Silica Gel based litter. It works pretty well, and seems to absorb most of the smell, except for immediatley after Tali has taken a dump, when an air freshener is very useful if you're in the house! It seems pretty economical, since only a little gets removed with the poo when you clear the tray. You have to leave it a bit after it's been used before clearing it, since it does suck up the liquids, and takes a while before that evaporates off.
The main downside with it is that it is very light, so very easily gets tracked around the house, although the vacuum cleaner sucks it up equally easily.
After experimenting, I'm not sure which I think is best, the Fullers Earth, or the Silica Gel stuff, they both seem to work fairly well, although the Fullers Earth does tend to form into lumps where it's got "damp"
so you do have to remove, and replace, more of it than the Silica Gel. It is half the price though, so much cheaper to replace. The bog standard CatSan was useless though, that's definitely not recommended.