In Canada the CEC requires:
120v with 12/2 loomex is fine. 20A breaker and 5-20R tamper proof receptacle.
If you run 20A 240v you will need a red jacket 12/2 loomex and a 6-20R tamper proof receptacle with 2 pole breaker. You will also have to buy a new cord for your sub. Using a normal resi receptacle with 240v is a big no no.
#10 for resi runs less than 30A is overkill, but fine if you have it around.
I wouldnt bother with 240v unless you know what you are doing. Follow the NEC in the US. Local codes supersede the NEC if the standard is higher.
