You don't say how many wedges you're looking to add or how far you currently hit your PW but I suggest adding 2-3 wedges that you can comfortably play the distances short of your pitching wedge. Given your handicap I wouldn't suggest anything with more loft than a 58* wedge as any more loft than that can get difficult to manage and is limited in how and where you can use it. If you were looking to add only 2 wedges I would suggest a 52* and 56* if you were looking to add 3 wedges either 48* 52* & 56* or 50* 54* & 58* really it just comes down to your full swing distance gaps. In regards to you having a shallow angle of attack and playing on firm turf conditions that just suggests that you should lean towards options with less bounce. That being said I believe it's wise to keep a range of bounce angles and not limit yourself to having only very low or very high bounce options. 

Maybe gap 6 deg?  Vokey 50 and 56?  I really like the S-grind.