Ok, 3 boxes, 4 cats, seems to me people spend more time cleaning multiple boxes than necessary.
We have 6 cats and only one box. The box is cleaned 2-3 times a day.
We use scoop-away and it works great. Not once has any of the 6 cats done their business outside the box (the box is a high-sided box and there's usually 3-4 inches of litter in it).
We're in a 2 bedroom duplex, multiple boxes just isn't feasable, cat accessories would end up taking up more room than the two of us do!
Used to be we had only 3, but took in 3 feral kittens from a neighborhood cat (neither mom nor dad were feral), kept them in the bedroom locked up and away from the other cats for about 3 weeks. They had us around at night and at other times while we got them used to us, then introduced them to the adults with no problems at all (at the time). Got the parents fixed, so they're happy now. Only problem is, we just couldn't give the kittens up, so now we have 6!
The adults are Mia (calico/tabby), Oreo (black/white and always looks like she's grinning), Mario (Siamese mix, not sure with what, but he's big and very soft of fur). Kittens are Leo (looks like a small lion, blonde tabby), then there's the two grey/white, almost twins, but can tell them apart by a small black spot on the nose of one. They are Simon and Garfunkle (Simon has the spot).