Help me set up my home, well, everything

[android6011]

So right now this is my setup:

- FreeNAS machine

- 2 x 1TB hard drive. (1 for storage, other for backup).

- 256mb flash drive for freenas image

- AMD Sempron LE-1250

- 1GB DDR2 800

- CPU usage averages like 15%, Ram roughly 18%

- idles at 50 watt power usage

- Mythbuntu HTPC (frontend and backend in 1)

- Intel Core 2 Duo E7300

- 3GB DDR2 800

- 160GB HD

- Nvidia 8600 GT

Originally I wanted a mythtv backend on the freenas machine, but then I go to thinking, why have on 2 machines at the same time just to watch tv. But then I also reallly liked the idea of having a machine dedicated to file storage, so thats how my setup came to be.

A main concern of mine is power usage, I am trying to keep the bill as low as possible. I am reapproaching the idea of having a separate mythtv backend, because I do want to schedule recording for when I'm away and would rather have my more light weight machine running than the other one. I have since installing freenas, fallen in love with it to an extent, it has been EXACTLY what I wanted out of a file storage machine, so I don't want to completely abandon it. (I mostly like the web gui and how I can physically control and software wise control the entire machine) I am considering installing mythbuntu backend on the freenas machine and running freenas in a VM through virtualbox. My questions are as follows:

1) All my machines are on wired gigabit, will a separate backend frontend experience any stutter for HD video streaming?

2) With freenas in a virtualbox VM, how would hard drive access, file sharing work?

3) relating to #2, will file transfers slow down even a little bit?

4) I have also considered having a more heavy duty firewall going, but again, don't want yet another machine eating power, how would incorporating this into the mix go?

If you think I am going about this all wrong, please tell me what you suggest. I am completely willing to scrap everything and start fresh (minus buying new hardware) except for maybe an extra NIC card if need or small things