My room is in the basement as well and close to the dimensions you have, 14x20x7. The one thing I really really wish for (in the next house..) is a higher CEILING. While movies sound a-ok, seeing that Hollywood has no clue how to mix a soundtrack, audio feels a bit constrained. Still good, but could be a more open sound with higher ceilings.
Audio room dimensions
I have and area in my basement where I'm going to build my audio room and have a couple of options. The easiest by far is to build the room to 12'9" by about 16' perhaps a few inches less on the 16. Or, 12'9" by about 19'. The latter will require I do some serious surgery to the area at the bottom of the stairs where the door at the bottom of the basement is. My question is: will the smaller room seriously compromise the sound vs. the larger room? The finished ceiling height will be about 7'. Thanks.