Pretty much all the big names (and some of the little ones) have sit down machines now. Handiquilter, Babylock, APQS, Nolting, Tin Lizzy, Gammill- all have sit downs. Figure out what features you want, how good your dealer support is, and what your price tag is. There is a lot of information about all of them.
That being said, I bought a Sweet 16 from Handiquilter a few years back. I used to live very close to the Nolting factory, and they were willing to make me one (great folks, BTW), but I liked the amount of support available for the HQ. I had to convince my dealer to let me buy it (they kept trying to sell me a frame setup), but they did a good job at setting it up when it arrived. I mostly get my support from the web, but some people need more hands-on help. Figure out your own style and go with it.
Pam