Good . . . that 1200kv motor with 11" props is a recipie for burnt motor (and likely would take the ESCs with it). That was a very poor selection, despite the advise you've recieved otherwise.
Those props will work well for the DT750's as others have mentioned on this thread, but *NOT* the 1200kv motor you've linked at 3S.
BTW, don't buy one set of props. Buy at least 3, consider buying 5, and be ready to buy more. The first thing you will break are props and you will break *MANY* learning to fly it . . . and many more there after, but at a slower rate. It really stinks to be grounded, waiting for another shipment for something as cheap as props. Also, learn to balance props ( and an inexpensive balancer is a good investement in making your rotorcraft fly nicer)
The DT-750 has it's quirks, but can be a good motor. There are better out there, but there are always tradeoffs -- it can stil be a fine choice. If you use the DT-750's, be sure to pick up a pair of nuts and washers for each motor, matching the prop shaft threading (I think it's M4, but check -- it's been a while). You will want to attach the prop to the shaft with one nut/washer above and below the prop, and a small gap between the bottom nut and the motor bell. Tightining the prop against the bell *might* casue the shaft to slip and when it does, it will burn out the bearings pretty quickly. The bell also tends to be poorly balanced, so it will vibrate until balanced with a properly positioned counter weight -- zipties can serve well for a balancing counterweight. It will fly without removing all the vibrations you can, but it will fly *MUCH* better when de-vibed.
Looking at your first post . . . the "OPTO" version of an ESC is lacking a UBEC. the way our power systems work, you plug the battery into an ESC (or all the ESCs in parallel) and they have a voltage regulator built in (called a UBEC). In addition to powering the motors, the ESC uses it's UBEC to provide regulated power for all the smart electronics. Effectively, Opto ESCs lack the regulator used to power your control board, reciever and servo. It's typically used in setups that have more than enough UBECs already or are electrically noisy and need external regulators and isolation (surprisingly, with as much going on in a multirotor, these aren't the worst).
You will need *AT LEAST* 2 non-opto ESCs to work with the kk2 board, since it has a divided power rail -- the power rail on M1 (used to power the board and reciever) is seperate from M2-8's power rail (which your servo is on). to powwer the board, you need one non-opto ESC connected to M1, and to power your servo you need at least one non-opto ESC on M2 or 3.
I'd nudge you toward a 30C or 35C battery . . . but the 25C will work. The 25C will wear out earlier (it will still last a while) and the throttle will start getting mushy and weak earlier in the flight time, where higher C packs will get closer to empty before you notice a significant performance drop, but overall it should work. I've found my 25C packs were rapidly joined by 30C packs (the 25C packs ran for quite a while after that, but the 30C packs flew better) and I've beeen slowly replacing my 30C packs with 35C (which fly even better).
If you get a kk2, buy a USBASP. You will need it to re-flash the board, and you will *WANT* to re-flash it. You don't need to buy HK's USBASP kit, but if you get one elsewhere (amazon, ebay . . . ), make sure you get the 6-pin adapter to go with it.
