I would, without a doubt, look at the Janome dealer and check out the new 7700 model. Upgraded from the 6600, there are a lot more features on this one and you can sew cuffs. The throat on this machine is longer so you are able to quilt with ease. It's not a long arm, but it certainly can do your quilting a lot better than any machine with a small throat. The work table is generous as well. Janomes are wonderful machines and considered workhorses. With the amount of quilting you plan to use it for, it will not disappoint you. I am not sure of the cost of this machine, but I certainly would aim at this model if you can buy it; maybe a layaway plan might help you afford this machine.
The fluke on the 6600 is that the base isn't removable to sew cuffs and pants hems. Not a problem for anyone who can sew because you can just figure out a way to do cuffs. I use my 6600 and feel spoiled because it's a superior machine from the 28 year old Kenmore I was working on. I feel privledged every time I turn it on and wouldn't give it up for anything unless I got the 7700.
Take your time looking for the right machine. You may even find the 6600 used at dealers and if you do, grab it. You won't be dissappointed with that machine either. Kenmore attachments fit the Janomes and so do some of the universal attachments and bobbins. No dealer will tell you that, but mine did. Also, if you have a good dealer who is willing to help you learn about the machine you buy, then you can expect good, honest repair service from them as well. Many dealers are just there for the sales and don't accommodate the buyer for anything else. If you are in the Lake City Florida area, check out Fabric Art Shop. The girls there will assist you with pleasure. They will also repair on site. That's where I got my machine and they are very nice.