The EPIA N (or Nano-ITX) is not yet available. It is very close to full production though and the current official release date is Q1 2005.
There are a few pre-production samples floating around (pretty close to the final product I must say) but there are no benchmarks AFAIK.
VIA announced 3 models : 533MHz (N5000), 800MHz (N8000) and 1GHz (N10000) all passivelly cooled.
The specs are very impressive and should outperform every known VIA mini-itx board :
MPEG-2 hardware decoder
MPEG-4 hardware assisted decode function
S3 UniChrome AGP 8X on-board VGA
DDR400 SO-DIMM memory slot
VIA Vinyl 6.1 sound on-board
SATA HDD interface
Mini-PCI expansion slot
With such specs it will be more than enough for what you want to do. As far as the PSU is concerned, two things are certain:
1. The board has a non-standard ATX power connector (will an adapter be included?)
2. The power consumption will still be very low, comparable to current EPIA's or even lower.
What will VIA decide about those matters is to be seen...
Take a look here for some pics of a working sample: