20 x 20' is good, as long as you have an additional place for your washer/dryer there also. Not too many windows, or windows on at least 2 sides so you can have the light w/o fading your quilts. I use those Joann folding tables with the brakes on their wheels (I put industrial velcro in the place where the legs go into the table top to insure the legs don't move when I don't want them to). Four of those is perfect for me (I've had them for 10 years now). You need shelves up to the ceiling for your sorted stash... the upper ones are for the "categories" you won't use often. I use a garage cupboard for larger pieces, stacked by color, and matching boxes for the "odd" things, like small (fat quarters) that are very specific (bugs, butterflys, trucks, buttons, etc.). Don't forget 10 or 20 stackable clear plastic storage drawers (in their own frames) for color separating your scraps (these are great because you can wiggle the drawers out and put the ones you are interested in onto your table and dig through them, matching up different fabrics). I also have an ironing board as well as a flat ironing board (I use old pillow cases for it's covering... just to give you an idea of its size). You must have a quilt wall... I use two insultation boards held together by an old sheet only so I can fold it into an 8'x4' space when I don't need it. Frankly, I'd rather have it 8x8 all the time, but I don't have the room for that. I don't put any distractions like radio or tv in my sewing room because I don't want the noise, but that's just me. If you are married you need to insert a husband who is proud that you quilt! Good luck with your plans!