What's the best strategy for upgrading CiviCRM?
Let me at least narrow some options for you:

The last idea of "sticking with 4.5.8." is not the way to go.  The Long-Term Support (LTS) version currently is 4.6 (and for the foreseeable future as of writing, see this question about the LTS jump from 4.4 to 4.6).  You will want to upgrade to at least that at some point (sooner rather than later since there are no more security updates for 4.5).  See this question for more about LTS.

If you want to try the latest and greatest, 4.7 is the one to use.  4.6 is the more stable route.