As most people here are saying, an EP kit would not worth the money. You will not gain enough from the expense. And with a 2" focuser, money would be better spent around that facility.
An EP kit would be fine if you didn't have eyepieces.
in your situation, you would be better served obtaining individual eyepieces. You can better control what you get, and not just take what you get.
An example is your 9mm plossl. You would have noticed that it has the smallest eye lens (the lens you look into. The other end of the lens system is called the field lens) of the three that you currently have. It is also the tightest to look into. Going to a 6mm plossl means an even smaller eye lens and having to just about park your cornea to look into it.
But for a little more cost than a 6mm plossl, you can get a much better eyepiece, also a 6mm, yet its eye lens is more than twice the size of your 15mm, and much easier to look into than the 15mm. And i am not talking about big bucks either.
If you are looking at a kit, it tells me that you might be on a tight budget. If this is the case, there are options available that will cost a whole lot less, perform extremely well, and if you take up just two or three of these, it will come in at less than the eyepiece kit, not three time the cost of the kit just for one eyepiece.
If you can give us an indication of your total budget, we can give you pointers as to what will serve you best. And if your budget is an open chequebook, you are in for a spend fest!
Filters can be very useful tools. Nebulae filters more so than colour ones. Which nebula filter? Have a read of the following filter guide. It details what the different filters can do. Understand this, and you can make a better informed choice.
http://www.lumicon.com/pdf/3filterspec_prnt.pdf
Which colour filter? These you really won't use very much. Really, you won't. Best i can suggest us you read the above filter guide, and decide on two or three filters, four at the VERY most. How these filters reveal features is sometimes counter intuitive, often very subtle, and always demanding patience and a learned eye to identify what is being shown. Read about filters. This will help you start to make better choices and understand what other people are talking about when they montion OIII, UHC, Broadband, etc.
Mental.
Edit - to answer your question about the difference between the two kits, the only difference is the price that i can see, and on is badged Celestron & the other Skywatcher. Skywatcher OWNS Celestron.