After shopping around for awhile, I decided on the Armarkat Cat Tower. It had a pretty substantial base, and if I left off the top tower piece, it would line up perfectly with our living room window. One cat could lay on the top perch and the other could easily lay or sit on the condo part.
When either one is feeling frisky, they also enjoy playing with the yarn balls. The cat tower actually came with five levels, but I only used four; the base and three more levels. It fits better by the window for us, with just the four levels.
The cats love it and couldn't wait for us to get it built. I think they knew it was for them. They were especially excited while I laid out the pieces on the floor.
This is the model that we purchased. We left off the upper post and top bed, as we didn't need or want the extra height.
There are other Armarkat Cat Tree models to choose from on Amazon. They come in varying height options, colors, and styles.
Update: The yarn balls have since come off, but the tower still stands sturdy and our cats still use it. I've since purchased little pet pads (kind of like a cover for a pet bed) and laid one on each of the top levels. Then I can easily launder those as needed to keep the unit cleaner and more fur free.
Cheryl Paton