I saw this article :https://blog.amasty.com/amasty-research-what-server-optimizations-for-magento-really-work/
So we installed Zend OpCache, and now its seems we are getting a stable TTFB of 0.3@robfico
Everything is being loaded into memory (IO system is relatively idle on the server)
Its the delay to the first byte was my concern as it was higher than 0.2 ( google recommend under 0.2), + other magento websites on the same spec server are getting under 0.2
My main concern was that the TTFB would get worse when we move over our main site to the new server/platform (more traffic). But I did concurrent users test and it seems to cope ok.
I think going forward we will try a Full Page Cache Plugin but are there any you would recommend for 1.9? (I noticed in the reviews there is a issue with Turpentine and magento version past 1.7)