Re: motor and esc recommendations for 4*
Sig itself suggests a range of motors/esc/number of cells in battery combos for this plane:
"500 - 800 watt Brushless Motor (800-1000 kv)
60-75A Speed Control (ESC)
3-4S 3000 - 5000 mAh Lipo Battery Pack"
beyond what stegl said, one consideration is the maximum diameter of the prop that will safely provide clearance of the ground.
Doing some reading on basics of electric flight, particularly around the relationship of Kv and battery voltage (number of cells), will help to understand what components of the drive system will work together. For example, if you went to a 6 cell lipo motor battery, you likely would be looking a motor with a Kv specification about half that suggested by Sig.
Using an electric flight predictor will help a lot, in my view, to understanding the relationship of many more components, flight performance and cautions of overheating. I use ecalc…… there is a free/demo version that shows how it works but the subscribed version (cost $6 U.S. a year) unlocks the full inventory of motors, batteries, props and esc.