to acquire what you are describing it will be over 10k HKD$
I would discount the Mac option as you have CS already for PC (unless it is a Wanchai Special).
I would steer clear of the Sony because they are a hassle and more expensive in the long run.
Someone mentioned Fujitsu earlier: an ex-colleague bought about 20 Lifebooks (?) for office use and they proved to be pretty solid and reliable. I think they are also a bit cheaper.
Otherwise you could look at the 2nd hand option.
So far it's come down to the choices among Mac, IBM and Sony - they are all over $10k if I am not wrong (not fit my initial budget but I don't mind if it suits the "best value for money" request). Like I said in the beginning, I just need it for basic use, no playing games or watching movies.
Now what do you say?
I say with those parameters you have very little choice so very little deciding to do. Style just take the bull by the horns and go and buy that laptop.