Hi Gunter
The ESC needs to be rated for a higher current than the motor will draw at full load, because even at part throttle the individul current spikes are still very high
The best of the cheper ESC's are any based on the Hobbywing chip, as they give decent performance, and handle a 400hz update rate.
Turnigy Plush, RCtimer are both Hobbywing based, and so are any of the hobbyking ESC's that are compatable with the Turnigy ES programming card (as those ones use the hobbywing chip) - but i would personally go with the Turnigy plush or RCT as I have had the best relability with them
A 30 amp is a good size to get, also important is the voltage rating, get one that will handle 4S, as quite often you end up going to a higher voltage, and you dont want to be swapping 6 ESc's
1.5kg hexa will take (worst case) 255 watts to hover, on 3S (11.1volts) thats 23 amps total, or bout 3.8 amps per ESC
If you used the RCT timer 750 kv motors
http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=523&productname= on 10 by 4.5 props and the 20 or 30 amp esc's you will be fine,
http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=146&productname=
you want to aim for hovering at about 30-40% motor power to hover to keep the heat down (as the airflow thru the motors is not as good as in moving plane)
so the above combo will be sweet,
total avilable thrust on 3S is bout 4.8kg so will fly your frame fine,
with room for a camera if you want to add one (dont go over total flying weight of 2.4 kg with that setup, you will need 50% power=75% throttle to hover, and the motors will run warm)
