I have Cornwalls, Heresys and KG4s
Both the Corwalls and the Heresys are 1980's ver 1.5 w/ resin horns and the same exact high and mid drivers... have no idea on the KG4s.
For better or worse all are completely stock w/ non-recapped crossovers.
All of them sound excellent ..and all of them sound different from each other!
My favorite by a good margin are the Cornwalls. They sound big, alive and have impact you can feel... and they require minimal power to get the job done. I power them with a 35 Watt Sansui 1000x.
The Heresys are closest in sound to the Cornwalls, at higher volume levels they have excellent tight "hit you in the chest" mid-bass. They can't go low (bass) like the cornwalls but are still very good. I power them w/ a 60 watt Marantz Model 15 dual mono amp.
The KG4s sound completely different from the Cornwalls and the Heresys... but again they also sound excellent, just different. I find the KG4s to be a very well balanced speaker with excellent full-range-ish bass response...actually the bass response can be quite startling for their size!
As far as what I have hooked up where... Cornwalls are in the living room and serve defacto music and home theater duty. The Heresys are in my home-office "listening space"... and the KG4's are sitting (not connected to anything) in the back of my old pickup in the garage lol. I need to give em a good freshen up (oil, etc.) and then hopefully find a permanent spot for them.
Quick Pros / Cons
Cornwall Pros:
-Effortlessly sound Big and Alive, serious impact you can feel!
-Takes very little power (comparatively) to sound loud and fantastic
Cornwall Cons:
-Size? ... I actually like that they're big
Heresy Pros:
-Sound very close to Cornwalls (that "heritage" sound?)
-Mid bass is VERY tight and can give you that great "hit in the chest" feeling w/ volume
-Aesthetic... with the tilted risers they look drop-dead gorgeous. Honestly, this a big reason they're in my office and not the KG4s.
Heresy Cons:
-Not as big and alive sounding as the Cornwalls...
-Low bass is indeed pretty non-existent. Careful EQ and room placement can help w/ this though.
KG4 Pros:
-Very well balanced
-Very good bass response...no special eq or room placement necessary
KG4 Cons:
-If I had to think of something I'd say maybe the midrange could be a bit thin when directly compared to Cornwall and Heresy... but just barely.