Marty,
> Is it more important to be in the center of the wall or to have consistant surfaces behind my speakers? <
It's much more important to be symmetrical (centered).
> My windows are covered with drapes would some 2in 703 behind the drapes be a good idea? <
Assuming the room needs absorption anyway, that will help.
> Would it be of acoustical value to open some of the drawers <filled with clothes> while mixing? <
Again, that may add a little absorption into the room. But in a room that size - and especially when the goal is to mix music accurately - you need much more than a few drawers full of clothes. In particular, what you need most is broadband absorption that's effective to as low a frequency as possible. Unfortunately, clothes and 2-inch 703 don't do anything useful at low frequencies.
> I have a bunch of vinyl records, should I utilize them as people do with bookshelves <diffusion>? <
A shelf full of LPs (or CDs) is not the same as a real diffusor. Perhaps it could be set up to diffuse a little, but you'd have to place the LPs very precisely. It's mostly a myth that a shelf full of "stuff" can be a good diffusor. And most small rooms need absorption much more than diffusion.
--Ethan
