5K is a *lot* of money! Instead of getting one machine that is all-singing and all-dancing, consider getting two machines -- one that can be busy automatically sewing out embroidery patterns for you while you sew on the other.
There is no one *best* sewing machine, unfortunately. There are pros and cons to every single one. You have to figure out what features are most important to you and make sure that the machines you look at have those features. With this amount of money, it is also critical for you to actually sit down and try out the machines before buying. You wouldn't buy a car model without a test drive, right?
Bernina, Pfaff and Janome tend to be the brands favored by quilters these days. For a long time there was a top-of-the-line Singer that seemed to be the favorite choice for embroidery, but I don't know if that is the case nowadays. Things change from year to year.
A good place to check for reviews is
http://www.patternreview.com . Joining is free, and then you get to read both old and new reviews of different sewing machine brands and models.