Yes the old black headed singers have much more space. Maybe not the cast iron 1941 verson!! I have an old electric and an old treadle. I quilted a pretty big quilt on the electric and it was a pleasure. Of course there are no bells and whistles on the older machines, but I wasn't looking for that.

Husquvana Viking makes a quilt machine that has a large throat.
It's made especially for quilters and has several other really useful things. Their walking foot has several different feet that clip on it including a 1/4 guide and a stitch in the ditch foot

I just bought a Janome 7700 Horizon and it has about 11" of throat plate. It doesn't have an embroidery attachment and is just a machine. Has lots of decorative stitches and three different fonts for letters. I'm loving how it works. Check out the topic on the BB and see what they say.

You might check out older machines. I kept my 10-year-old Bernina PE140 because the harp area is 9". My new PE230 is 8" and that 1" does make a difference. My PE140 is still a good machine. I keep it clean and have it serviced periodically and have never had a problem with it in 10 years.

I think they are the same.

If you go to the Free moting quilting site she tells you how to quilt with a normal throated machine. She suggests scrunching instead of rolling. Her explanation works!
http://www.daystyledesigns.com/articles.htm

Vintage Singer 201's and 15-91's have just shy of 9 inch harps. Don't forget about the height of the harp. Just because the bed is longer, if the machine arm takes too much top room you will still be limited to what you can fit under it.

Husqvarna has sapphire models with 10" opening

If you dont want to spend a lot of money you might look at older machines. my 1975 model kenmore has a 7+ inch opening and I have little trouble doing a queen size quilt on it. also the price was right when I got it (free)just needed cleaning, oiling, and a little rust buffed off a few spots.

Three years ago my DH bought me the machine of my dreams or so I thought. I have the Bernina 440 Quilters Edition with the stitch regulator. I thought that must be great for machine quilting. I didn't realize what was meant by "long arm"
My machine has a 7.50 arm. I find it really hard to do free motion quilting. Live and learn, if I get another machine I will know what to look for.