my machine is sitting on a folding table. I put it on a non-skid shelving and also gave it a good cleaning. Found a very tiny piece of lint that made the bobbin case move also. I have a magnifying glass I use to go over after cleaning. You would also be surprised what you find if you turn the lights out then use a flashlight and find lint in other places of the machine.

Another thing If you are using a card table, you can get a piece of wood or even a large wood kitchen cutting board to help stabilize the machine.

I've tried various new machines (bought it, took it home trying it out, then returning it) in my price range and have been much happier with my dependable workhorse. Not really wanting to go outside my comfort zone on price.
Putting a mat under your machine would surely help with the bouncing. Have fun with your new room.

You have a lot of good advice for helping stabilize your machine on a tabletop but I think you should still celebrate the new room with a new machine. :) Keep the older one to take to workshops and use the advice given here to keep it from dancing. I am a Pfaff fanatic but if I have to buy a new machine I think I would look seriously at the Janome. I do have an older Janome that is great and have friends with newer models. They have not had any problems with their machines and I have "borrowed" theirs when I am at their house and agree they are fine machines.

My machine bounced when it was on a table without much support underneath - when I changed it to the other side of the table it stopped bouncing.

I use a carpet stair tread under mine. It helps.

Go to Wally World and buy a 1/4" foam rubberized mat. The mat is in the rug section, I believe. I bought one for the quilt shop, cut it into thirds and placed it under 3 of the machines setting on those plastic tables. It really cuts down the bouncing. Brother is coming out this fall with a rubberized machine mat just for that purpose, but the Wally World one was only around $9.00 and did 3 machines.

The padded dish drainer mats work great for a machine pad. A machine on a folding table needs to be set at the end over the legs, not in the middle. The table will shake, even if you bolt the machine to the table.

A brother PC-420 is mostly metal so should be more solid you can get them from all brands or amazon for 360 and up depending if buying new or refurbished all brands.com is a dealer with great reputation. The plastic ones tend to move a lot because they are so light in weight

I have this mat I bought a long time ago. It's been under my machine so long I forgot about it. I need to order another to take to classes. http://www.cottagemills.com/default/...achinemat.html