Well you are right a KAC SR25 is the top of the line .308 rifle.
That said 6,000 to 10,000 is a lot of money for a semi auto production rifle no matter how great it is. If you were lookning at a semi auto SIG550 or FAMAS or high end Steyr AUG I can see spending that kind of money because those weapons are no longer in production or can not be imported. And anytime you are spending that kind of money it would be better to buy a tansferable machine gun than a semi auto
So that leaves the DPMS and Armalite. I do not own a .308 AR, have HK91s FALs and a Springfield M1A but no AR10.
However, I have one friend that owns a DPMS LR and another friend that owns a Armalite AR10. I have shot both and I have to say that between the two I would buy the DPMS.
It is very accurate, MOA or better with certain loads. It is also less expensive than the AR10 by a few hundred dollars, and the DPMS is based more on the Knight SR25 and uses SR25 mags. Armalite mags are expensive because they are modifed M14 mags...but they are become more affordable. DPMS mags were VERY expensive during the AWB, but now they are around $30.
DPMS also has a great customer service should there ever be a problem.
Chris