KG and GB are right on Syntagma Square, super close to all things downtown and plaka. I've never stayed at either albeit having had coffee there or so but oddly will probably be doing so following week. I have stayed at Academias which is couple blocks from former properties, very nice smaller boutiquy Autograph place. The neighborhood is grafittid but safe (close to University). There, you are nestled between Kolonaki and Monastiraki... Stayed at New Hotel on Syntagma Square as well...not the grandness of KG or GB and rooms are a little unique in design but very comfortable and you are basically right in the Plaka zone.