Ok Megan,
Nice little set up there.......The Pioneer blu ray was seen to be very good in it's day, and the speakers are very good, as 'style' speakers go....
To me, and I had an Onkyo 606 before my Denon AVR2310, the weak link is the receiver, unless you like the 'brute force and ignorance' style sound the Onkyo's produce?
Personally, and I use this system for 2 channel music too, the Denon 2310 was much better than the 1910, and way, way better than the 607, when I demo'd them one after each other.
If it was my money, I would upgrade the receiver to something a little more than the 1910 (it's very good for the money, but the KEF's deserve more, in my opinion). The Denon AVR2310 or Yamaha 1065/2065 might be a really good upgrade......and keep the blu ray player for a while.
Lastly, if you have more spare cash, I really recommend upgrading mains cables, speaker cables and inter connections, if you are using 'bog standard' ones....