Yes, the 6ga wire will handle it just fine. Your tub may be different, but mine has 2 dual speed 6 hp. pumps and a 6k watt heater, it pulls a lot of power when the filter cycle kicks on both pumps and the heater is running. So per the mfr., a 50amp breaker is required. And yes, the outside disconnect box needs to be 10 feet away per code. When I had a few electricians come out and quote the job, I was quoted between $500-$800 with materials for this job.