As promised here are my stats on vmware 4 vcpus siege -c50 -b -t240s -i 'http://127.0.0.1/test.html'
gzip off, pagespeed off.

Transactions: 898633 hits
Availability: 100.00 %
Elapsed time: 239.55 secs
Data transferred: 39087.92 MB
Response time: 0.01 secs
Transaction rate: 3751.34 trans/sec
Throughput: 163.17 MB/sec
Concurrency: 49.83
Successful transactions: 898633
Failed transactions: 0
Longest transaction: 0.03
Shortest transaction: 0.00

If you want to paste your considerations on my stackoverflow question http://stackoverflow.com/questions/19160737/nginx-fastcgi-cache-performance-disk-cached-vs-tmpfs-cached-vs-static-file

I'll pick it as a correct anwser.

Now i'll set up static gzip serving and use comp level 1 for dynamic content.

Thanks alot. Best regards