I was about to make a new post to share this info but I found this. Your question fits quite well with what I was going post so here goes...
First, to answer your initial question, I have the Dell T320 running FreeNAS as an iSCSI server for my VMWare cluster.
Power: I'm currently running 6x 1TB 7200RPM enterprise SAS drives. The machine is currently sitting at 84W and usually stays under 100W most of the time. It is very efficient on power.
Proc/RAM: Not much to say here. I have the Xeon E5-2407 and 4x 8GB DIMMs which is good enough. There are six DIMMs total so I could expand the memory a little but haven't had a reason to yet. I don't really need much more, at least in my use case.
Network: I'm running one 10Gbe DAC cable from an AOC-STGN-i2s card to a cheap Fiberstore switch and it works well. You can probably get away with 4x 1g, but make sure you buy a PCI NIC because the machine only has 2x ethernet ports onboard.
Expansion ports: It has quite a few PCI slots. I can't remember how many off hand but enough to add NVME drives, NICs, SAS cards, or whatever else you want, except GPUs.
Hard Drive backplane: It holds 8x SAS or SATA drives which is awesome. There is also a built in USB port on the motherboard which is hidden inside the case. I use this for the OS drive and it doesn't take up a HDD slot or external USB port.
Storage Controller: Let me start by saying the H330 is a marginally better card than the H310 and probably doesn't have the same issues. My research before going fowards with ZFS showed that people were complaining of the H310 card not performing well in HBA mode in regards to multi-disk read/write performance. I was previously running the H310 in a RAID10 with four 1TB disks and it didn't perform well that way either. To fix this issue, I flashed the Perc H310 with the LSI 9211-8i firmware. There are tons of threads and websites that have written endlessly about this so please just research it yourself and make sure you understand what can go wrong before you do it.
OK, now that I got that out of the way, time for the good part!

Once you flash the LSI 9211 firmware onto the H310, the Dell iDRAC has a fit about it. Since it can no longer detect hard drive temperatures, it decides to set the front fans to an annoying and unnecessary level as a failsafe. I'm sure a lot of people who did this didn't care but my server lives near my desk so this was an issue for me. Looking online, I found a few people griping about it but not a lot of solutions. One solution I did find was setting the fans to a static setting (like 20% fan speed all the time). I didn't agree with this option as it would require tweaking and monitoring and I knew there had to be another way!
Well, there is another way. After reading through pages and pages of documentation from Dell, I stumbled upon the RACADM manual. RACADM is accessible by using SSH to your iDRAC port. You log in with an administrator account and type "racadm" into the console.
So the important bit for this is stuffed all the way at the bottom of
this page here.
For people who don't want to translate Dell's language, here is the command to run. Just SSH to the iDRAC IP, log in as root or a user with admin rights, and run this command:
racadm set system.thermalsettings.ThirdPartyPCIFanResponse 0
And with one line of code in the right spot, I was able to get rid of the annoying noise for good

. I'll admit I haven't tried to reboot yet to see if it is persistent. If it isn't, I'll just script it.