Well, just a matter of reading lookup tables once you know the details. Basic Math when you get the right info. Experts correct me if I'm wrong but.
For lookups to determine if the wiring is sufficient gauge just know the current, gauge, length of run:
1. Run length
2. Gauge of wire (8 gauge)
3. Panel voltages, amps which multiplied together gives watts
* My panels info is 8.15A, 30.7v, 250W (30.7 x 8.15)
Home Depot: Grape-Solar-250-Watt-Monocrystalline-Solar-Panel-with-Black-Frame-
Run in series I just up the voltage, parallel up the amperage. The sum of the multiplications adds up to 500w. I was going to run them in series. The charge controller TS-60 says it can do up to max "Solar voltage" of 125v. My two panels in Series would be a max of 61.4v. Should be good. Just need to look up the chart for 8 gauge stranded and see if the length is ok for those values. Charts all over the Internet but it looks like for about 15A @ 12v 30' 8 gauge should be ok.