NAS advice?

[Sean Crago]

I'm now the proud adopted father of a 60GB Playstation 3, a native
DLNA-compliant UPNP player. I've had an N800 in the house for a while
too, so it'd be nice to be able to start utilizing those capabilities.
My current desktop dual-boots and stores most of the files that I make
available over my home intranet on a pair of removable hard drives.

I'm torn, however, between buying a hardware NAS (Can any of them
really handle transcoding a decent variety of codecs?) or building a
Solaris/BSD box.

The NAS I'd stuff with three or four newly purchased hard drives,
preferably purchased separately. If I were to build a
Solaris/OpenSolaris/Nexanta/FreeBSD/whatever box, I'd be running a
JBOD ZFS array with the two pre-existing drives (gutted from the
removable chassies) and two new ones that are each twice the size of
the older ones. If I were to go down homebrew road, we'd be talking
about an Atom, a Nano, or some other reasonably low-power processor
and motherboard - As long as I get enough performance to saturate an
802.11g connection, I'll be fine. More interested in being able to
stretch out its life on a UPS.

The added flexibility and the massive cost savings (largely from the
JBOD capabilities) of the going the homebrew way seem nice, but does
anyone have any words of wisdom about problems that I might run into
trying to run a decent transcoding UPNP server on an OS with a mature
ZFS implementation (ie, presumably not Linux just yet - I'm not
running a four disk array under FUSE), or point out any other concerns
that might push me towards an off-the-shelf NAS?

A few other concerns that might influence what I ought to do:
1: My house is concrete and brick throughout, with basically no way to
run CAT6 without punching holes in the floor. As such, the wifi
connection is most likely to be the interface that all this stuff runs
off of.
2: The current drives I'm using are about a year and a half old. If
you think I'm better off getting all new drives, that's fine - I can
sell my old ones easily enough here.
3: I'll definitely have the new NAS behind a UPS, regardless, but
Kathmandu is "down" to 12 hours of rolling blackouts from last month's
high of 16 hours/day, and I'm not about to burn enough of your tax
dollars in my generator to keep the house powered up 24/7. Unattended
shutdown or, at the very least, the ability to safely recover from an
abrubt shutdown is an absolute necessity.

Thanks,
Sean Crago
Kathmandu