Thanks guys, for the advice so far.
The Realtraps products look more like they're for optimizing your room and not so much soundproofing, but that's an interesting web site and I'll be visiting it again just for the educational stuff. Thanks.
Since this is just a rental, I don't want to do anything too extensive or costly. If I owned the place, that would be a different story.
I've thought about renting a modest place and having a separate rental for my studio, but I've looked around and it wouldn't be practical. I live in one of the most expensive parts of the country (Oakland, CA) and even a small, run-down place in the ghetto is $800-$900 a month. A decent, safe one-bedroom is in the $1300-$1600 range. Renting a studio space is like renting another apartment.
Here's a link to the floorplan of the apartment so you can get an idea of how isolated the kitchen is. As you can tell if you read the details, the place has a lot else going for it and is a little hard to pass up in favor of living in a basement:
http://www.watergatesales.com/html/wg-02.html