You must then have a very early '94 because most '94s on up didn't have them at all. Volvo dropped them from the cars until more recent times with S80s in '98. '93 850s did have them but many were removed after the fastening holes eventually became stripped out. At any rate, you don't NEED it at all and it just gets in the way when changing oil.
As for the IPD version, do you need that? You've been OK w/o one for 10 yrs now so rocks hitting the oil pan hasn't yet been a problem. Oil pans are usually cracked when the car goes off-road (accidentally) but that'd be the only time when you might be saved by having that.
The most volnerable part on the front of the car is the radiator which is just under the bumper, supported by plastic ears which is part of the radiators plastic side tanks so when someone gets too close to a high curb, they often hit the radiator, break those ears off and the radiator leaks. Not even IPD makes protection for that.