Like Derek said, Is this your DD, or your weekend car?
I love my Z, and as much as I hate to say it, performance parts can wait for a little bit. I'm focusing on making the beast more comfortable to drive and getting it to look a little better right now. I'll have an alarm, AC, a full stereo system, a new interior, and all of my body work+paint before the summer is over so I can take it with me as my only car when I move across state this fall.
Power windows would be a great addition to a DD, along with power door locks, but if your Z is your fun sports car that only plays a few times per week then no ac, manual windows, and that luscious scent of gasoline and old vinyl that we have all grown to love is the only way to go