Glad to hear you got some of the stuff home now. Not to mention a nice little collection to start off with. This is when the fun really starts.
I recognize a couple of the freight cars you have. The "Virginian" hopper, what looks to be a "Tropicana" box car, and what looks to be a "Heinz" box car. If that's the case, those are likely Tyco "brown box" cars. If they are, in fact, the Tyco cars, they will have the couplers mounted to the trucks.
Those are a bit of a difficult conversion. I recently acquired a few from my father and made an attempt at converting them. The result was a lot of derailments and uncouplings due to loose couplers that wouldn't return to center after a turn.
The currently installed couplers should work fine with what you already have. I would save the conversions for chassis and/or body mount couplers.
As for actual coupler selection, those that you have listed (they are the #5 couplers with a medium center shank. Most locomotives and rolling stock use these.) are a good baseline coupler. However, each application may require a different coupler (IE: some require a long underset shank, others require a short overset shank, etc...).
To determine if you need a center, offset, or inverse offset shank, a coupler height gauge comes in very handy. Kadee also has a chart listing the part numbers for each coupler type. Here's Kadee's listing for them:
Height Gauge
http://www.kadee.com/htmbord/page205.htm
Coupler Chart:
http://www.kadee.com/htmbord/HO-Scale%20Couplers.htm
It's always good to have several of each type on hand. This will allow you to test fit each type of coupler you may need (though the chart will give you a base idea of which coupler you need). Start with the #5, then check your coupler height. If the coupler is dead on, no further action is needed (except for bending the air hoses up if they don't clear the base of the gauge). If the coupler is above, you need an overset shank. If the coupler is below, you need an underset shank. The length of the shank will depend on how far underneath the car/loco the coupler box(coupler mount) is. Once you know the shank type you need, then you can reference the chart for the part number.
Short answer to your question IMHO:
It'll be a good idea to have those couplers on hand, and bulk is the cheapest way to get them. However, save them for your new locos and rolling stock as you acquire them unless it's a chassis or body mount coupler.
Enjoy,
Shannon