It sounds like you are looking at the right series of tractors. The 3000-20's are too small for round bales and the 5103's are a little clumsy for mowing. Also the 4000-20's have more US content vs 3000-20 (Japan) and 5103 (India). My 4120 easily handles a 6 ft rotary cutter (rhino SE6). Do not forget to get your rear tires loaded to help with those round bales on the front loader. The prices you show look good if they include a 400X loader.