And how about...

[UKenGB]

http://www.ebuyer.com/654664-gigabyte-b ... -bxbt-2807

or

http://www.ebuyer.com/614389-intel-nuc- ... n2820fykh0

or

http://www.zotac.com/de/products/mini-p ... llery.html

All very similar hardware, but MM2 compatible?

I prefer the idea of a small square box rather than the flat Asus EEEBOX which covers a larger area. So the above would suit and I like the MM2 concept of network booting and easier 'one shot' upgrades. But can MM2 be persuaded to run on them?

I want 4 or 5 of these frontends so they need to be reasonably priced.

[warpme]

http://www.ebuyer.com/654664-gigabyte-b ... -bxbt-2807

or

http://www.ebuyer.com/614389-intel-nuc- ... n2820fykh0

or

http://www.zotac.com/de/products/mini-p ... llery.html

Well - I believe all of above should work fully plug-and-play.
I'm not sure about BIOS PXE in above machines - but it is highly probable that they can be booted via PXE.
Unfortunately all are Intel HD graphics based - so no any nice denterlacers.
Generally regarding graphics: best is nvida. AMD is OK. Worst is Intel.

Nvidia:
-best picture (IMHO, YMMV)
-best playback (silky smooth)
-best stability
-full deinterlacers support (including smooth double-frame rate with advanced motion compenstion)

AMD
-good picture
-good playback (mostly smooth)
-good stability (mesa instantly improves)
-full deinterlacers support (but double-frame rate isn't smooth; disqualified for me)

Intel
-picture worse than nvidia/AMD
-good playback (mostly smooth)
-good stability
-only basic deinterlacers support (no double-frame rate at all; disqualified for me)

All very similar hardware, but MM2 compatible?

I prefer the idea of a small square box rather than the flat Asus EEEBOX which covers a larger area.

It can be placed vertically

So the above would suit and I like the MM2 concept of network booting and easier 'one shot' upgrades. But can MM2 be persuaded to run on them?

i think one thing is will MM2 run on it; another thing is how good/smooth video playback will be.
First thing is mostly MM2 dependent and currently we are supporting 1180 gfx cards and all major CPU/chipsets. Should be OK for majority.
Second thing is mostly GNU/HW gfx vndors drivers + MythTV dependent thing. Here nvidia clearly rules.

I want 4 or 5 of these frontends so they need to be reasonably priced.

I know Your pain.
Nevertheless I'll go for (from best to worst):
-ION/ION2 (even second hand)
-small-factor AMD with integrated gfx
-Intel (gfx wathever; all are not acceptable for me)

[UKenGB]

The problem with ION is its no longer available and although finding 1 or 2 secondhand might be possible, if I want more than that it becomes a problem.

What about this Zotac, it's got an NVidia GPU:-

http://www.zotac.com/de/products/mini-p ... tions.html

[stuarta]

The NUC makes a lovely frontend, I use mine natively as a frontend, ie. not via MM2

[UKenGB]

I did take a look at NUC, but I do want to use MM2 and it would be such a beautiful partnership if it ran on some of the current Apple TV lookalikes.

No matter, I've picked up a few Acer AspireRevos that I know work well with MM2. Just waiting for them to be delivered and the first tuner card for the backend server. Once I have all that I can actually try it all out.

[warpme]

I did take a look at NUC, but I do want to use MM2 and it would be such a beautiful partnership if it ran on some of the current Apple TV lookalikes.

There is absolutely nothing prohibiting running MM2 on NUC.
I'm guarantee You: MM2 will use FULL capabilities of NUC (in other words: it will run no worse than other distros - and in some places it will run even better than alternatives).
MM2 additional bonuses are:
- there is no any install need
- in majority there is no any config needed
- OS/myth/whatever upgrade on any number of front-ends is by single copy only 2 files on central web server

I'm advising Nvidia over NUC only because:
-NUC gfx gives noticeably worse picture than Nvidia
-MythTV is not supporting Intel's VPP (so no nice 2x DI for interlaced content like TV)

As You see - both aspect have nothing with MM2!