Firstly im not sure Pakistan will actually get the Spruances, they are a single mission ship and as such totally unsuitable fora budget semi-regional navy, they will most likelly go for 2 or 4 Oliver Hazard Perry multi role frigates.
Secondly the equipment that the USN has been using on the Spruance class may not be all sold to Pakistan. I would think that at the very least the sonar would be downgraded and the helicopter would not be as capable as the USN version.
Thirdly, even if Pakistan was to get the Spruance and all the equipment (unlikelly) the fact remains that they have no experience whatsoever operating against new generation Hunter Killer subs, and believe me there is a big difference between an Akula and any of the other deisel electric rubbish that is beeing used in that region currently (with the exception of the Kilo and some of the later generation European submarines).
The way you fight a HK sub is totally different to how you would fight a deisel electric. The main difference would be that a deisel sub can only really protect a spot in the ocean. It is not really very effective at activelly seeking out an enemy force. They simply do not have the speed or capacity to make long distance high speed movements as they tend to need to surface for air rather quickly when moving at anything over a snails pace.
To summarise, a deisel will sit in a certain spot, move a little and pretty much attempt to place itself in the path of your surface group. If you deviate toomuch from that path it has no real chance of stealthily catching up. A HK can set up an ambush, attack, retreat and then do it all over and over again, or if the captain is particularly evil it could even use thermal layers in the water as well as its performance to get into the enemy battlegroup at point blank range and cause havoc. something a deisel has no hope in surviving.
