PaperPrincess and Onebyone have given you great advice.
As you can see, there are a lot of excellent machines out there and each one of us swears that their machine is the best. I am a Pfaff person myself, but I have had and sold Vikings, had Babylocks and have a featherweight. I love the IDT that Pfaff has (Integrated Dual Transportation aka built in walking foot) and would not sew without it. The real answer is that they all make (for the most part) good machines.
Make a list and prioritize it. Try out lots of machines and choose one based on features, cost and the ability to have it repaired locally if the need arises. Do not neglect to look on Craigslist - a lot of time you can find a machine locally for a good price. If you go the route of purchasing from a dealer - DO NOT hesitate to bargain. I was amazed when I worked for Viking the deals they would make. If it is not negotiable on price, they can throw in walking feet, acrylic tables all sorts of stuff! Good luck with your search.