I run a fairly similar server; make sure you are getting unbuffered ECC RAM. It was a bit of a pain to find, but I also wanted 8GB sticks (maxed it at 32GB).
You can mix and match the SATA ports. That MB/CPU combo will allow you to passthrough the M1015, so that is your easiest route. For the onboard SATA ports you can RDM them to the guest, or just make them vmfs datastores and allocate them to the guest that way.
My esxi host (32GB, E3 1230v2):
Server 2012 standard (file server, running flexraid with M1015 passed through to it)
Ubuntu 12.04 (plex)
Ubuntu 12.04 (newznab) - dedicated 2TB HDD
Ubuntu 12.04 (sab/sb/cp)
Ubuntu 12.04 (gallery3)
All of them sit on a 250GB Samsung 840, with about 70-80GB free yet.
Plex doesn't seem to have any issue whatsoever with the files stored on a different system. Had a heck of a time trying to get newznab running to the share, so I ended up giving it its own drive, and no more issues there. Performance is snappy, have yet to have any performance issues with any guests, and still have quite a bit of legroom for further growth and/or sandboxing.
In my case my servers are on 1 subnet, and my clients are on another, with pfSense handling bandwidth throttling so my downloaders don't kill my internet connection when my wife is trying to browse. This adds the complexity that now my LAN traffic must go from ESXi to pfsense (outside the virtual network) and then back into ESXi; been thinking of just letting ESXi handle the networking to avoid this, but not sure Ill really see any difference.