The 450 isn't being discontinued for now. I've got a 440 and 820, and I do find it easier to get a perfect 1/4" on the 440, with the more narrow feed dogs. Other folks swear that the 9mm feed dogs are no problem. So just try it out for yourself. I'd recommend getting the 5.5 mm stitch plate (accommodates the wider dogs, but has a smaller opening). It still allows you to move the needle or use a non-straight stitch, but doesn't tend to draw fabric down the hole. I use the 5.5mm plate more than the straight stitch/single hole plate on my 820. Good luck, enjoy your new Bernina!