can you add a second rad to Waterchill ?

because it has a controller for the oem unit can it be upgraded to add another Rad? and still controll it? or is the rad completely not controlled at all?

Sorry a NOOB to liquid cooling. for like 430 cad i can get a dual rad waterchill kit up and running.... but is it worth it or should i custom one up?

and with a budget of like 350 us what would you do?

350 USD is alot for water. You could add a second rad to a water chill but it would kill flow rate. I'd get:
white water/RBX
L30/Eheim 1250/mag3/DD12V/swiffy 600 thing
tygon tubing
metal hose clamps
dual 120MM fan car heatercore
maze4 GPU