i would recommend nex5n instead of nex3 since u highlighted .although its a little off ur budget,u shud each model u listed out above.
instead of 550d , i recommend 600D. its rm2500+/- .I used my friend 600D b4, its kinda fun and simple. As for a35,it has much more customize-able effect . evf is  , u can see ur setting on ur view finder .

Canon 600D is nice if u have small hand. but if you have a large hand ,you will feel that its kinda uncomfortable to hold it . Personally ,i recommend a65 since u prefer nikon and sony.

video -600D is good in af /mf.
        -A65 is good ,but it comes with continous af

both have better video compared to d90. It easily heat up the camera .

D90 for rm2500 is not much recommend as warranty is not available.
since your budget is rm3000 below and you mentioned  ^. i recommend you have a try on a65. it is much advanced compared to a35/a55.