Can anyone recommend a Net-Top with HDMI output?

I'm preferably looking for :

Barebones,  I got loads of Memory & Hard Drives kicking about
Nvidia Ion Chipset : I want this to be able to play HD Movies (720P max)
Low Power (This will never be turned off)

I've seen the Foxconn nT330i which looks interesting, not bothered about physical looks, as I'll mount it to the Vesa mount on my TV.

I love my Revo R3610 but I know that's not what you're after

I love my Revo R3610 but I know that's not what you're after

If you're struggling with HD content on that, you can get a Broadcom MiniPCIe decoder card for about £40.

OK, So lets assume I'm going for the Zotac ID11 (Intel Atom D510 Dual Core, Nvidia Ion2 Chipet).

I've got a 500Gb SATA II Western Digital HDD ready to go in.
So, we're on the topic of Memory.

This box will be either running ubuntu or Windows 7. XBMC, SABNZBD, uTorrent, Sickbeard and CouchPotato.

The question is Memory.

Do I go for 1, 2 or 4GB Ram?

The most stressful thing this PC will be doing is extracting Rar/Par files and decoding 720p MKV Files.

I'm sure it's still 2.5".  I've got a load of 500Gb Drives spare
http://pden.zotac.com/index.php?page=shop.product_details&flypage=flypage_images.tpl&product_id=240&category_id=118&option=com_virtuemart&Itemid=1

I'm hoping if the ION2 is going to be taking care of the decoding, it doesn't matter what SAB does in the background with the Atom.
I could get away with a tiny drive in the PC, as once SAB has done it's bidding, I've got scripts that move the files to my various NAS.

You looked at the asrock ones? They look pretty slick in gloss black. From memory you can squeeze 2 hard drives in them aswell.

The guys over on forum.xbmc.org seem to love the Acer boxes but can't remember which model.

The lowest specced machine I've got everything working on is my netbook which is Atom 1.6 single, 1GB ram (3GB now), ION1 - This plays everything I throw at it including full BluRay 1080 dumps (30GB+ files) but obviously it depends what software you want to run on it.

Running something like Media Browser over Windows Media Centre (7) will obivously require something with a bit more power than a XBMC live install.

I've borrowed the Zotac Z-Box box off a work mate before and both of us agree it gets WAY to hot to leave on 24/7.

Depends what you want from it

24/7 box thats just going to be a media/DL box then I would just stick a XBMC live image on it (can run Sick Beard, Couch Potato, SabNZB as addons for all your DL & sorting needs) but if your going to want it doing other things then maybe a full Ubuntu / Windows install running the media program on top (which will be slower but on the CULV chip not by that much).

As for Boxee vs XBMC all I can say is try both and see what you prefer. I tried boxee, it had more things out of the box, was easier to setup, harder to modify, good media scrapers, looks good out of the box on a large screen far away.

XBMC is harder to setup, crap internal scrapers, looks better after personal tweaking, larger addon community, runs better on the low end.