I am in the process of putting up my Viking Designer 1 for sale....a thing I thought I would never do but like you about a year ago I decided I wanted a machine that I could use soley for quilting including improving my FMQ.
Things I looked for were....Good FMQ ability, Bigger harp to actual get the quilt in for FMQ, Needle up/down position.
I ended up buying a new to me Janome 6600 for approx $800 (£500...am in the UK)...in truth it took a bit of getting used to as it is very different to the Viking......but a year on I really love this machine and wouldn't swop it for anything including the 7700. Along with the above features I like the accufeed, needle cutter, the lighting, the sturdiness of the flatbed, the huge sturdy extension table, the thread holder.....infact my list is endless. The only thing I miss from the Viking range is the 'pivot' capability....but I hardly even think about it now.
The stitch quality is lovely and FMQ is very neat.
I have used the Viking for embroidery for the last year, but a couple of weeks ago had the opportunity to buy the Janome 11000 very reasonably....again am very happy with it. It is set up for embroidery at the moment but is very easy to change to domestic sewing.
I still think that Viking make wonderful machines but for patchwork and quilting I think I have become a Janome fan.