The best replacement for 2.6 is 2.9 ghz.

The best alternatives to 2.6 are rated as following:
★★★★★  2.9 ghz
★★★★  2.3 retina
★★★  2.3 macbook pro
★★★  2.3 mac mini
★★★  3.0 kernel
★★★  2.7
★★  2.7 python
★★  2.4 macbook pro
★★  2.3 ghz
★  2.7 macbook pro
★  2.7 macbook
★  2.5
★  2.3
★  2.4
★  1.3
  gimp 2.8
  3.2 kernel
  windows live movie maker
  xecuter 3
  macbook pro 2.3 retina

Your alternative for 2.6 is not listed? Suggest!
Speaking about 2.6, one probably shouldn't forget about luxrender.

Other search terms related to 2.6 and their ratings are:
★★★★★ luxrender
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Google Trends

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2.6
2.9 ghz
2.3 retina