Lastly, it might be fun to invert the ATC speakers or run them on their sides, perhaps with tweeters outward. This will change the system somewhat and lend variety to experiences. Of course companies will not advise, but this is your system and it's all fun. Take a look at my virtual system and you can see I tend to play around with such things as speaker position in order to get different experiences with soundstage.  Such experimentation is informative as to how sound fields are influenced by design.  

Also in regard to the ATC monitors, consider a method I have used and endorse - in fact, using it now with a set of Wharfedale Opus 2-M2 speakers - which is to double (parallel) speaker cables, running two sets. It is a most efficacious improvement that keeps the character of the sound, but enhances it notably. 

Just make absolutely sure all connections are perfectly parallel, no crossing over of terminations at amp or speakers. I triple check such connections and never change gear when tired, because mistakes can be made.  Typically I keep on hand both spade and banana terminated speaker cables for that purpose.  :)