DC-10s should be replaced with either 767-400ER or A330-300. Both aircraft have similar range and seating of the DC-10. I would avoid the B777 unless you can actually BUY the aircraft. If you lease it, compare the cost of the B777 and the A330. Is the price worth those extra 5-10 seats.
If you plan to operate any other type of 767, then going with the 767-400ER will have the same commonality.
If you plan to operate A340's, then A330 will also have the same commonality.