Mulley,
My first upgrade (of many) beyond a Sony HTiAB system was to step up to Def Tech 800 speakers. These were eventually moved to surround duty and replaced by Def Tech 1000s up front. I liked both and each was an improvement over the previous set-up. However, overtime I found the 800s inadequate to properly fill a room size of 18' x 13' x 8' ceilings (carpeted floor and a couple fluffy couches).
Therefore, I would recommend the 1000s as a minimum, unless your room is quite a bit smaller than the one above.
Cheers,
XEagleDriver