Wilson Alexandria x2 series 2 vs XLF vx Alexx?

Just curious for those who have heard these wilson speakers. Has there been substantial sonic improvements as you go through newer speakers? Or are the sonic improvements fairly subtle?
The OP of this thread :
My Long List of Amplifiers and My Personal Review of Each! | Audiogon Discussion Forum
has been on a long journey through some very high-end gear.  He currently has the Alexx and I know he's had other Wilson speakers, so you might want to check out the thread and maybe ask him,
Paragon has the Alexx and the Alexandria X2 both. I spoke to them about both and decided to order the Alexx. More musical they said. 
I listened to the Alexx at Take 5 in New Haven.  Jaw droppingly good sound driven by Ayre's Reference gear and an Esoteric DAC.  One of the best sounding systems I have ever heard.   Not sure how it compares to the Alexandria, but with right amplification, they are incredibly impresive speakers.