I'm a bit confused on the difference. I can obviously see the cosmetic differences, but are they internally the same? I've been playing through my singers 810e for the past few months and have been looking for a used one to pop up. Well, I found the 810av used for $600....I'm kind of excited because for once I have the money, but I want to know if there is any major differences. Also, is this a decent used price? Thanks in advance for your advice and expertise!!!