One thing to look at in embroidery machines is the embroidery field. Meaning the size it can go up to and down to. (smallest/largest)
I have a Kenmore Ergo3. Sews and embroiders (up to 4 1/2")
It works great for me and you can find them brand new on ebay for under $1000 and some Sears stores still carry them.
I know Janome sells a nice one as does Pfaff, Viking and others.
You should go and try them and compare.
I have a friend who used Quiltsmart interfacing for the wedding ring quilt she made. Said it was easy and fun and came out perfect!
I'm sure they sell the size ruler you need. Maybe call a quilt shop and ask if they have it or if they can order one for you