Thanks for the advice! While I do agree that the BL18s are the most suitable for a hifi system, what I meant in my comparison - is to ignore the streaming capabilities as they would not be an influence on my decision. If I were to go with the A9 for example, I would definitely use the inbuilt streaming (ie Spotify Connect) and use the line-in for Vinyl and CDs.
The BL17s are looking more tempting now though :)