Well, I'm not sure how anyone is reliably advising you without knowing ...
- Is this going to be for 1 website, or multiple websites (reselling)?
- What is the full exact server specification?
- What are your targets for traffic (hits, pageviews, bandwidth commitment)?
The advice we give to our customers ...
If you need to re-sell hosting
Nginx > Apache > PHP-FPM
That keeps .htaccess support for your customers, security (chroot/multiple php.inis) from PHP-FPM and static file performance from Nginx.
If it is just for you
Pound > Varnish > Nginx > PHP-FPM
This gives you SSL unwrapping from Pound, static and dynamic (ESI) caching from Varnish, un-cached static content from Nginx and dynamic content from PHP-FPM
If you've got no real experience with Varnish
Apache > PHP-FPM
Our typical architecture is ...
If it helps, for web clusters, we typically use:
lvs (initial ssl load balancing)
-> pound (ssl-unwrapping)
-> varnish (caching)
-> haproxy (load balancing)
-> nginx (static content)
-> php (dynamic content)
-> mysql (db)
The truth is that you can do a lot more damage than good with Varnish if you do not set it up properly (cached private sessions, unwanted cookie un-setting). The same applies to Nginx.
Have a read of this http://www.sonassi.com/knowledge-base/magento-kb/mythbusting/why-shouldnt-i-use-nginx-for-magento/ and this Building an SSL server farm
My final advice, consult a professional - its money well spent.