I think it's really important to know what you want out of your machine. I notice that the newer, less expensive models have much smaller work areas between the needle and the motor than older machines. If you want more area, then you have to spend beaucoup bucks to get that larger area.
I have a late 60s Singer FashionMate and LOVE it! It is a work horse. I was taking a dart in my jeans waistband the other nite, and it sewed it like it was a piece of cotton. My machine straights stitch and zig zags, and I can move the needle L/R.
If I did a lot of machine embroidery, I can see the advantage of the computerized machines.
Personally, for $400, I'd be looking at CraigsList and dealer for trade ins to get the best of a vintage model that i could fine. I am not sure $400 would get me much on a new machine.