A Few Questions on Doing Fresh Installs.

I'm about to wipe my D: clean.  I currently have FS9 and FSX on there with a lot of add ons.  I'm going to re-install FSX fresh on this drive after uninstalling everything and I have a few questions.

Is it really necessary to reboot (after defrag) before installing Acceleration?  I have FSX Gold.  I keep hearing this but I know there are people who follow NickN's stuff and others who don't.  Just wondering what you guys think.

I'm actually thinking, maybe, I might try an SSD if I can find a cheap 250G.  If I go with SSD, I never have to defrag, right?  I can just install FSX/Acceleration and one add on after another? 

My next question is regarding FTXG that I'm going to purchase.  I also have Ultimate Terrain X.  Does it matter which one I install first?

And my final question is about REX2 and Active Sky 2012.  I have them installed and running off an external USB 3.  Can I just leave them there when I uninstall FSX or should they be re-installed too?

Thanks