Are your temps good as is? If they are, I would say don't mess with what works, but you could also try a remount of the block, a remount of my old air cooler netted temps 4 degrees cooler, which is pretty good for 20 seconds of effort.
No idea about the nozzle kit, I also got it with mine, but have yet to actually try and install it.
General reports suggest that you might get a degree or two using the nozzle kit, but that's about it. Possibly more important is the washer that comes with the kit which 1) fully seals the upper chamber, and 2) increases the block's bow a little more. It increases the block's restriction considerably, but you've got a pretty strong pump already.
If you're going to pull the loop apart, and you haven't gotten one yet, you might consider an aftermarket top for that pump, such as THIS. The DDC-3.2's can benefit a great deal from the top's, since the stock intake is rather restrictive. And if you use the nozzle kit, the top could help offset the reduction in flow.
i7 2600K | ASUS Maximus IV GENE-Z | 580GTX | Corsair DDR3-2133