Here's a blog entry about what to look for in sergers.
http://shesasewingmachinemechanic.bl...blog-page.html
We sell Juki and Bernina sergers where I work. The Juki 654 is a great machine that runs about $500. The Bernina 1150MDA is a nicer machine that costs about $1,100. Both have built-in rolled hem, tall thread rack and differential feed. The Bernina 800 DL runs around $900, if you can find one -- they've been discontinued by Bernina. The Juki air threader MO1000 kinda scares me, because if the air threader gets clogged, you can't manually thread your machine.