Thanks all, that's actually very helpful. I did look at celeron + discrete options (I think I looked at a G550 + HD6450) and it did work out a fair bit more than a Llano based system at local prices. I'll have another look at the numbers though. What's the minimum celeron you'd recommend?
I do like the fact that I could upgrade to an i3 or i5 if I took that path, but TBH I'm not sure I would - and with the price of the llano components I could probably sell them second hand and just replace the motherboard\APU at a not huge loss - looks like I could reuse most of the other components.
Ultimately I'm still leaning towards Llano.
The other decision is a4-3400 or a6-3500. a4-3400 seem quite a bit easier to source over here than the a6-3500 - I've found a couple of places with the A6-3500 in stock, but it looks like the a6-3670k is a lot more readily available, though almost double the price of the a4-3400. ($70NZD vs $100 vs $120 for a4-3400, a6-3500, a6-3670k respectively)
I think 2D to 3D is not something I'm likely to want to do (My TV does have an option to do this I think - would the HTPC do it better?) are there other common activities where the a6 will be better than the a4?