呢排好多4pk放出來..

3PKS, ~2900
new FASST C2, 2X faster,
with drop wheel,
battery and charger

Very attractive

For the 2x faster question:
A simple google search result (for those lazy guy who like to ask question):

http://2.4gigahertz.com/systems/futk4901.html

1st line:
"With much lower latency (up to 2 times faster than the 4PK) ..."

(Hope this is one time only, I'm not a teacher who like to teach others, or tell other what to do)

For the 2nd question?  Don't know and don't care.
(Heard that KO 2.4G have some reception issue.)

$2900 expensive ?  I'm seeing people switching to 4PKS, there must be some reason behind.  

Anyway, there are cheap cheap cheap GT3B, only $300 HKD (or less ?) for those who like low price.
"hundred goods for hundred customers"