Best close to a wall

Easy a pair of Proac Tablette 10 on the end of your Xs they will sing 

I once bought a pair of A5s without listening to them, just because they were cheap, so I knew I could sell them on if need be. I couldn't believe how awful they sounded, and took them to a dealer, thinking they must have been faulty. They weren't, so I sold them and bought a pair of X2s, which were a huge improvement. I should point out that this was the earlier A5, not the A5R, so maybe they have improved.

The X2s are a little more than 6" from the rear wall, but not much, and seem to perform very well in my room. 

I too have X2's and similar to Chris are a little more than 6" but again not much. They are a great speaker and work well with Naim, my dealer highly recommends them but do dem at home. In my room mid and treble is lovely but bass can bloom if not careful. 

My experience of the original A5s was that they sounded exceptionally boring.   Your mileage with the A5r version may vary.

The original A5 was probably the worst speaker Spendor has ever produced.  The A5R is a massive improvement, but I believe still quite room dependant, even if not so position sensitive.

IBLs obvs. 

I listened to the x2 at a Naim  event held at my dealers.They sounded absolutely beautiful on the end of gear lower down the ladder than mine.At that moment I would of bought them there and then but took them home the next day for a extended home demo.what a difference,after less than an hour I knew they wouldn't work in my room,the bass was just way to boomy and totally uncontrollable.I liked them so much in the shop I was convinced it was something in my system causing this.I  tried homemade foam bungs in the ports but still couldn't tame the bass boom.I eventually ended up with bowers and wilkin's pm1's that sound amazing to me.

The moral of the story I suppose is as we know speakers are so room dependent I think a home demo is a 100% must for speakers.

I use a pair of Rega RX3's they are positioned approx 9 inches from rear wall. I have tried them in different areas of my music room when I have been moving equipment around. They are very versatile when it comes to placement in my experience. 

They have a mid bass driver at the side of the speaker, in my set up I prefer to use the speakers with the mid bass driver on the onside of the speaker.

I do think X2's need careful room matching. In the right room/system are wonderful. I have had some similar issues as Scooot....speakers eh!