Dear wittaj and EMPIRETECANDY,
What you say sounds most sensible. However, it is not so easy to buy SD5A425XA-HNR in Russia. On the other hand, SD50432XA-HNR is very easy to buy and it costs not so much, around $500.
Also, I am afraid SD5A425XA-HNR is much more visible when panning and tilting...