You have many options for skipping the posts, but the basic room sizes are pretty much set for you. The posts won't really make much difference.
One thing that stood out in my mind was the 14"-8" x 21' option. You want to stay away from room sizes that are multiples of any given number. Seven is a common denominator for the dimensions you listed. You did not list a ceiling hieght so I assume you are going with an eight foot ceiling. Which is fine.
Given the options you listed I would suggest 12'-6" x 22'. I know that it is hard to get it into your mind that you will be building a smaller room, but it should sound better than the other combination of dimensions.
If you would like more info, check out Robert Harley's book "The Complete Guide to High-end Audio" or visit http://www.rivesaudio.com both of them have some very handy info for determining room size and sound quality. You should have Robert Harley's book anyway, just for the helpful info in it.
One thing that stood out in my mind was the 14"-8" x 21' option. You want to stay away from room sizes that are multiples of any given number. Seven is a common denominator for the dimensions you listed. You did not list a ceiling hieght so I assume you are going with an eight foot ceiling. Which is fine.
Given the options you listed I would suggest 12'-6" x 22'. I know that it is hard to get it into your mind that you will be building a smaller room, but it should sound better than the other combination of dimensions.
If you would like more info, check out Robert Harley's book "The Complete Guide to High-end Audio" or visit http://www.rivesaudio.com both of them have some very handy info for determining room size and sound quality. You should have Robert Harley's book anyway, just for the helpful info in it.