Just remember that the 4x4 doesn't really sew a 4x4 letter. I think about the largest I've gotten on my Brother machine is 3.94x3.94. I have the combo SE270D which is the Disney machine. You will also need a separate lettering program if you want to do various styles of lettering. I love Monogram Wizard and it is so user friendly.
I buy most of my machines factory refurbished from Ken's Sewing Center in Alabama. Great service. They ship the refurbished machines from TN distribution. I saved about $100 per machine. They sell on eBay and they have a website. wwwkenssewingcenter.com
Also, Allbrands in LA has great prices also.
To check out the Monogram Wizard lettering software go to
www.sandscomputing.com or
www.needleheads.com They have a lot of the popular styles and you can download a demo before you buy.
Good luck and happy hunting!!