If you're not having any issues with the TX/RX then I say do the 401 first also you don't need to get a digtal servo right off you would be better off buying 2 HS65s (pitch / roll) instead of the digtal and then when you get another 200 dollars by the DX6. I upgraded my 35 to what you plan on and the biggest upgraded was going to the 401. I never had the stock Walkera TX/RX I started with the DX6. The gyro made flying a whole lot easier wish I would have started with it rather then a cheapo. The S75s are nice but they are a bit weak and don't return back to exact center as nice for the pitch and roll. Good luck.