There's also the option of hanging them on the wall...tail draggers work good for this...just a loop of fishing line around the tail, hung on a small finish nail!
My main display room is roughly 12x12...I have 210 models displayed!
When I finished off the basement, the "built in" cabinet and shelves were more than enough to house my stash and all my builds (many of which are gone now). I have run out of room several times...add a couple shelves...add a couple more...add a couple more.
And...the cabinet barely holds just my 1/72 stash now!