so far i havent heard any non-original racket of Li-Ning.
Perhaps u can ask more expect here

http://forum.lowyat.net/topic/806445

LN is good but is there such model as N5? or you mean N55 or N50?

30lbs is the limit where factory/supplier is providing warranty
logically, the higher tension it can withstand, the better the material is used although this might not be suitable for some cases
LN's quality should be ok

to get more power, a flexible shaft is suitable
anyway, before buying a new racket, you can try lowering your tension to 24 or 23lbs
might give you more power
too low tension is not good either

control would come when you're used to the racket you're using and have better technique

just my 2 cents opinion