Sub feeding

Set me straight if needed. I'm going to sub off of my 200A panel and go to a detached metal building I have erected. Have studied and viewed post here and at other sites for my needs. I plan to go at it this way, I will be exiting the 200 amp source panel with a 125A two pole breaker, going underground in 2" PVC conduit @ 24" depth, conductors are copper @80' long, (2) # 1 line conductors (1) #1 neutral conductor and (1) #6 insulated ground. Of course we are also unbonding the sub panel since it was cheaper to buy a main load center. Also, an 8' driven rod and # 6 solid copper wire will be used for grounding the sub panel. Is anybody going to try and ask me to use #2 wire and save on cost??? Or should I stay with #1 because of an amount of voltage drop in the 80" conductor run and for future needs. Surely I could have went with a 100 amp panel and used #2 but the future or perhaps the next owner may have more needs. Also, since I have not bought any equipment yet and I was thinking about sub feeding to a 200 amp panel in the detached building, is there any limitation for the size of the sub feed breaker coming out of my meter panel (source). I have reviewed all of the nomenclature and data at the source and it no where states the maximum size of breaker that can be used on the busses below the main breaker. I am under the assumption since the busses are fed by a 200 amp main, then they are rated for 200 amps for sub feeding. Of course from what I know, 150 amp is the largest breaker that can be added to my source panel. The only notation in my box states, " Use CU Only Conductors At Branch Circuit Breaker Terminals Rated Greater Than 90 Ampers". At the store, 200A load centers were the cheapest, if I bump the wire up, I could get at least 150 amps to the building. Appreciate any input.