The 400XT seems to be a very satisfactory match for the Alfa models – in particular check Dora9’s blogs and posts.
However it seems you are keen to try the CDR motor – is it because it is a more powerful motor then the 400XT? (I’m actually not familiar with either)
Personally I use the MP Jet AC 28/7 35D MkII – the “big blue”with an APC 9x6 in my P47 Pengie. This motor has plenty of speed for the lightweight Alfas and I spend most of my time cruising around at half throttle or less to keep the speed reasonably scale and to avoid having to constantly turn to keep the model in sight. With this motor I have to be very gentle on launch due to the torque – about a third throttle with firm toss and then slowly bump the throttle up as the plane gathers airspeed – nonetheless it will still roll to the left as the throttle is increased. I lost my Alfa Corsair due to too much throttle on take-off - it torqued over, I stalled the wing with big aileron inputs trying to correct it and it crunched into the ground. The Corsair was a beautiful plane to fly, and the financial controller just gave me permission to order a new one – payment for polishing her car