Well, that sounds a bit better.
10600 is 1333, not 1066, so your base speeds are compatible. Now you have to concern with the other timing portions of the RAM being compatible.
If it were up to me, and I was intent on using both kits together, I would just install the new set, fire up the machine, and run a RAM test overnight, or at least for a few hours, and verify all of the RAM modules are returning good data and no errors. If you get errors, the machine locks up, or otherwise fails to complete the tests as expected, then I would set out to either find compatible timings between the two kits, or simply stick to the new kit, as it's much larger than you are currently running and should handle pretty much any task perfectly fine.
MemTest86: http://www.memtest86.com/
Memtest86+: http://www.memtest.org/
Windows Memory Diagnostic:
http://windows.microsoft.com/en-us/windows7/diagnosing-memory-problems-on-your-computer
If the tests run without error, most likely you'll be fine with both kits installed and no custom timing.