[ale] Lowest Power MythTV back-end?

[JD]

This question is for all the MythTV users.

The Myth-wiki talks about recording 480x480 resolutions
http://www.mythtv.org/wiki/Hardware_Requirements#Performance_issues . That is
like a TiVo Series 2 from 2005.  Not exactly useful for today.

What is the lowest power box that you'd recommend capable of recording 3
concurrent 1080i streams?  Specifically, the
* CPU
* RAM
* Disk subsystem

I'd rather not throw a Core i5 or SSD at this problem, but worry that an
Atom-based system just won't have the necessary power. Perhaps I'm completely wrong?

Existing components for this build are:
* HD Homerun HDHR3 - network tuner (may add another)
* Hauppauge 950Q - tuner (not used)
* GigE network - rock solid
* Blue 1TB HDD - just for recording, not long term storage

Does running a Myth backend inside a VM work well?  I'm doing that with 7MC and
end up with stuttering in some of the recordings due to HDD performance inside
the VM with just (2) 1080i streams concurrently recorded the HDD is a WD-black.
I could throw an 80G raptor at it, but don't really want to.

An AMD-E350 box could be repurposed (Atom equiv) and know that an dual core Atom
N280 can't handle 1 HiDef recording, much less 3.

Suggestions?  TIA.