Suggestions for Cox network.

So things are changing in the house hold. New guest moved in and trying to start a mini business in my basement. Here is what I thinking:

Arris TM1602(24x8) > Ubiquiti ERLite‑3 > NETGEAR ProSAFE 8 > 3 RG6 Solid + RT-N66U(AP) + Ubiquiti UAP-AC-LR-US

RJ11 to phone block with 2 jacks plus test phone at eMTA. Everything will be powered by a Cyberpower UPS. Right now it's direct from ground at D-mark to modem. Great signal levels. Rx is a bit high so I may want to split and keep eMTA for phone and SB6190 for data. Or even move the SB6190 to a CB account and keep the eMTA for Resi HSI. Depends on how things go with the business. I won't actually running the site from home until I get a CB or other account. Maybe FIOS? Gigablast? It's a good 6 months until things really get going but a lot of work to do. Suggestions? Thoughts?

I am building a "server" basically for home media and internal use, but later may go public. Should I get a dual NIC Mobo so I can use it as a firewall or will the ETLite be enough? I am concerned about IPv6 firewall. 

Last, anyone here a builder? Trying to put together a Frankenstein build with a 500w power supply I had from another build with case and everything. Just needs AMD CPU cooler and HDD. Should I invest in that or spend the money on a refurb desktop for a more modern CPU socket for upgrade? Future proof vs frugality.