I see you asked the same question on Audio Stream.
As you know, the XEO 4 is based on the X14a and uses the same drivers. With the XEO 4 you are getting on board DAC's, active crossovers and a power amp for each driver. The XEO also has the benefit of on-board DSP settings to help with room placement, such as positioning near a wall or room corner. The X14a misses out on that facility.
The larger floorstanding XEO 6 sounds very good indeed and the few reviews I've read for the XEO 4 give no cause for caution or concern.
The only downside is the limitation on the use of Hi-Res files (the Hub accepts up to 24/96, but transmission out to the speakers is limited to 16/48). However, bearing in mind the arguments about the dubious merit in anything above 16/44.1, if you are happy with CD quality, this shouldn't matter.
Save on those speaker wires and the cost of an amp. Sound quality should be on a par with the X14a, if not better.
Note: You could also later on add a XEO Link to feed another system, or active speakers elsewhere in the house.