A "pre-loved" Viking SE should quilt at least a queen sized quilt. They were top of the line about 4 years ago have been supplanted by the jewel line (Diamond, Ruby). They are really good machines which will let you piece, quilt and embroider and the price is down to $2,000-$3,000.
The biggest thing to look for is a reputable dealer. You can go in and test drive all machines of any dealers within a reasonable distance from where you are. They should give you a couple of free classes after you buy and they should have a repair person on premises and hopefully be around for years for service.