Yes, the Heresy speakers will be a major step up. I went from a pair of Cerwin Vega's to the Klipsch Cornwalls myself. You do not need a whole lot of power to drive them, as the first responder said. If you do have a SS amp, you just won't want to play them really loud, as it will definitely be harsh - tubes will work better.
Everyone talks about horns on the loud end, but one of the many things that is so great about them is that they are also amazing on the soft end of the spectrum, again especially with tubes. They simply can't be beat for their dynamic range, all over the spectrum.
