Here is some info from Bernina UK about the 500 series, Jill. I can't find something similar for the 400 machines. They are the Auroras and are going to be phased out as far as I know. The 600 series is also no longer produced. I guess if you like the Auroras it would be a fairly small step up (except in price) to the 500 series, and the same from the 600 to the new 700 (except that there is this chance of the new 700 series possibly coming with a larger throat space).
B 530 - Creative Sewing
This machine is ideally suited to sewing or repairing clothing – jobs which require high needle-penetration power. It is excellent for home furnishings projects, dressmaking and gifts.
You can use the BSR foot (BERNINA Stitch Regulator) which is an optional accessory on your B530.
With 150 modern, high-quality stitches including alphabets, both practical and decorative stitches pre-programmed on the machine, it is ready for any creative challenge. A variety of high-quality buttonholes are included.
An illuminated LCD display shows all settings and provides help where you need it. Direct-selection buttons enable quick stitch selection and let you adjust stitch length and width. An easy user guide is there for beginners or those returning to sewing in their creative projects.
B 580 – Creative Sewing, Quilting and Embroidery
The 5 Series top-of-the-range model is supplied complete with embroidery module; the BSR foot (BERNINA Stitch Regulator) is an optional accessory.
The maximum stitch width is 9mm.
The modern high-resolution graphic touch-screen makes using the menus and functions so easy. This market leading touch-screen, the software, sewing machine and user guidance are perfectly matched to one another.
A few simple steps enable you to choose from over 230 preprogrammed stitches with ease. The 100 embroidery motifs included along with this model are also quick to find and to embroider. All of these embroidery motifs can be edited in many ways directly on screen and saved easily.
The B580 can be operated by the supplied foot control, or by the start/stop button. The speed control enables the right sewing speed to be set manually for different sewing projects.
A bright, long-lasting LED sewing light illuminates the work area, a big help for long evenings' sewing.
A threader swiftly passes the thread through the eye of the needle and there is a practical thread cutter which always cuts the thread to the right length.
The 5 Series all have an ideal thread guide, even fabric feed and high needle-penetration power. Reverse sewing is engaged at the touch of a button. The supplied extension table and the freearm offer even more convenience and ease when sewing.
Each sewing machine comes equipped with useful accessories, its own carrying bag, and a storage bag for all the supplied tools.
B 550 QE - Creative Sewing and Quilting
The Bernnina B550 QE is for creative quilters. Whether you are an experienced quilter or setting out on your first quilt creation this machine will satisfy your creative aspirations.
The sought after BSR (BERNINA Stitch Regulator) is included for highly accurate freehand work.
Nearly 200 stitches are pre-programmed into theB550 QE with a choice of alphabet, practical and decorative stitches, special quilting stitches and a variety of buttonholes. A button sew-on program is included and there is an illuminated LCD display.
Helpful support from the user guide ensures trouble free sewing