Is value is a function of what you use the computer for.
If you do a lot of AV encoding/decoding, then it makes sense. Perhaps gaming will get a small fps boost as well. Otherwise, the 2.3 is just fine. Don't pay attention to those who blindly recommend it without even asking what you use the computer for. If you're doing regular computer stuff (browsing the web, document creation, iTunes, etc.) 2.3 is more than enough. You'd never feel or appreciate the extra 10% from the 2.6.
If you can list the applications you use on a daily basis, a proper recommendation can be offered.