XigmaNAS

I'm expanding my storage from current 14TB to a 30TB system. (8 x 3TB Z2; 3 x 4TB Z1; 3 x 2TB Z1; 5 x 1TB Z1)
My existing hardware is an ML110 G5 based board fitted into Norco 4224. Current RAM is 6GB ECC DDR2. Max supported upto 8GB only. CPU is Dual Core E2160 1.8GHz

Can I survive on an 8GB ECC for 30TB Storage on ZFS for the next 2yrs with NAS4Free? Hate to throw away my ML110 G5 hardware.
I overan budgets with Norco 4224 / 2xM1015 / and 3 HDD's failing & ending up buying total of 6 new HDD's with shipping costs amounting to more than equipment - yea I'm far away)

The rule of thumb for ZFS is 1 GB (ECC) RAM per 1 TB of HDD space, and there are just three rules to get ZFS perform well:
1) add enough RAM
2) add more RAM
3) if you think you have added enough RAM, add some more RAM
So, it probably will work but you might get performance issues, if ZFS has not enough RAM and needs to store the cache and meta data on the disks instead of RAM.
I personally would advise you to get a new board and at least 32 GB RAM for a 30 TB setup.

What kind of performance issues am I to expect with 8GB? I mainly hoard content. Stream only to the foll: XBMC Media PC; iPad; VMWare Store

Meantime - appreciate cost effective recommendations to start working on. (I have 2xM1015's so I want to use them; Just bought my second M1015). Your Avaton looks too convincing now. Save the PCIe limitations. I might hit upto anywhere between 45~80TB in future - unless someone comes up with cheaper, smaller & simpler forms of high tech storage.

What kind of performance issues am I to expect with 8GB?

In the worst case you get a kernel panic and system halt, because ZFS needs RAM to cache data, for the checksum calculations, etc.
For sure you'll get a decrease in performance on heavy ZFS usage.
Some claim 8GB is the absolute minimum for a home NAS, but your 30-45-80 TB are currently more than the average home user has.

Kernel Panic = Data loss & ZFS corruption or mere halt on high transfers? (I dont use jails, dedup or compression)

Does the below make sense? fits under 500$. Though I'm not fully sure about the i3 & ECC. Shows supported on Intel website.

SuperMicro X9SCL-O (155$)
http://www.newegg.com/Product/Product.a ... 6813182252

Intel Core i3-3240 (120$)
http://www.newegg.com/Product/Product.a ... 6819116773

Crucial 2x8GB ECC UDIMM PC312800 (180$)
http://www.newegg.com/Product/Product.a ... 6820148770

Still a little too less RAM but better than just 8 GB. You can later on add another 16GB if needed.
The i3 will do for NAS purposes, otherwise go for the Xeon.

Attached system status of my current 6GB ECC with 20TB storage live. Ongoing RSYNC in background moving files.

How do i find out when it begins to hit ram llimits? Didnt see anything in logs.

The 1GB of RAM per TB of storage is really only for medium/large business or very heavy utilized NAS's. There are plenty of people that run with far less than that without any problems. For a home 4GB is a bit low, but 6GB shouldn't have any problems. Have you tuned your NAS for the amount of RAM you have using the ZFS kernel tune?