I presently presently a Bernina 830 that has a BSR (Bernina stitch regulator) and would recommend the Bernina as well as the 450. I purchased both used. Bernina is a quality machine and I think with the BSR your stitches will improve. I also find that I cannot FMQ w/o my gloves with the nubbies to grip the quilt. The gloves are available at the LQS.
My local dealer is great about trade ins. And Bernina corp. has a plan that for many months, you can have interest free credit for your purchase. Ask about both.