I don't see the point in all this to-ing and fro-ing. Curry is an example of exchange cooking, the meat and the spices exchange flavours over time. This means it benefits from taking time. Time to simmer the meat in the sauce and (where possible) time for it to rest in it too. Curry is better the next day. Pressure cooking is quite counter productive in regard to flavour development.
If you want good curry grind (and in some cases roast) your own spices freshly and take your time. This does not apply to foods that cannot stand long cooking like seafood and some vegetables. But you wouldn't pressure cook them either - I hope. If you keep a library of whole spices you can make a huge variety in flavours and styles of dishes from many nations, if you use packet/bottle sauce you are stuck with their formulation. If you buy ground spices they will often not be fresh when you get them and will always lose freshness on the shelf.
The only benefit is see in the packet sauce and pressure cooker combination is time. Even if you are very busy you still have options such as making curry on slower days that can be eaten then or on busy days when you don't have much time to cook. If you cannot make time to cook you have my sympathy 'cause you will miss out on some good food experiences. Exchange cooking does not require much technique, anybody can learn to do it well. If you enjoy curry and spicy food DIY.
Enough theory, the practical side of it is all the spices you need will be found at a good Asian grocer. These are often run by ethnic Chinese who may or may not know anything about curry spices so you will need to know the names of the stuff you want. Take care that some recipes are westernised and substitute or omit ingredients, this doesn't mean the food will be bad but it is worth trying these things as they are traditionally made before deciding if you like them that way or if you don't need to go to that much trouble.
Without getting into an argument about what constitutes authentic regional cooking I offer two reliable sources of data. The online encyclopedia of Gernot Katzer here and the work of Charmaine Solomon, an Aussie author and journalist born in Ceylon, after 40 years her books are still in print and include recipes and details of the properties and uses of the ingredients. There ought be more OAMs given to cooks!