I have a Viking 1+ which did a 4x4. I bought the larger hoop - 5x7 - but never used it. I think the designs for this hoop had to be split.
So when I decided to upgrade, I looked for machines with much larger hoops. Specifically, I wanted approximately 8x8 and 8x10. Figured that buying once was cheaper than buying as I outgrew embroidery field sizes.
I chose the Babylock Ellisimo. (Yes, lots of $$ but it was my gift to myself after years of catering to everyone else's needs.) I also considered the Janome MC11000SE which is also a very nice machine. My reason for choosing the Babylock was that the technology was several years newer and I didn't want to wait for the new Janome coming out this fall.