I was torn between the S16 and the Tin Lizzie sit down. I was ready to buy the HQ but ended up with the Lizzie in the end because I really just liked the way the machine was orientated. I haven't regretted my purchase at all.
Having said that the HQ sewed beautifully and there's a lot of room. It's 2" shorter than my machine but I'm sure it would be the same more or less. I've free motioned 2 king sized quilts since getting it. It's awesome. The extra space makes quilting so much more relaxing.
You'll want to get tables to go along side the table that HQ gives you. My Lizzie came with an extension table off the back. For the HQ you need the extension table to the left of you so it will hold the quilt. HQ sells a small extension table but it was big bucks in my opinion. I have a skinny folding table to my left to support the quilt and it works great.
If you can, try as many sit downs as possible. If you have a big quilt show coming up, it's worth the wait to try out as many machines in one day as possible... Oh - and this spring Juki is releasing their sit down long arm. I have to say that after using their stand up, I would have probably bought the Juki sit down instead of my Lizzie. I love my Lizzie but I'm a Juki girl
Yes, I've considered selling the Lizzie to get the Juki but I don't want to take a huge money loss so I'll stick with what I got for now at least