In my opinion personally,
The best motor for the XXXNT is the Thunder Tiger EVO .12! They are cheap and are insane fast! The local hobbytown has 5 or 6 of them for like $80 or so... Easy to tune... Hold a tune well... And they rip it up!!!
But thats just my opinion... I had one in my AD2... It was way too fast for me at that time... Definitely too much motor for a newbie....
Thats my $0.02