Mike from a brief look thorough of the review there are two critiques.
Firstly you failed to emphasise sufficiently that a Phenom (well more specifically HT3.0 or rather at least 1.6ghz) is necessary for full deinterlacing options (possibly other post processing options but I'm not certain of that) with the IGP. Since this was apparently one reason a Phenom was choosen in the test platform (before I noticed your hidden away comment in the review I guessed it may be and it seems from your contact with AMD it was) it's IMHO a bit silly to critique the processor choice all over the place and then only mention one of the key reasons in one paragraph in the middle of the review. (I didn't even notice you mentioned it the first time I skimmed thorough the review but noticed in at least two places your critique of the processor choice). Remember this is supposed to be a HTPC, if all you're watching is Blurays I see little point of it personally (just buy a standalone). (Although I've seen from elsewhere that some do, perhaps it's just the nature of TV in the US)
Sadly Phenoms are rather power hungry even at idle but the alternative is to add a discrete graphics card which of course adds to the cost. Technically the Sideport memory may be able to make up for lack of HT3.0/1.6ghz but if this is possible (this is pure speculation on my part from what I've read) it hasn't yet been implemented in the drivers AFAIK. Admitedly even with the HT3.0 the post processing (particularly of SD content) is somewhat weak compared to a good standalone (e.g. HD4650) and you possibly need to disable Aero so perhaps a discrete GPU would have been better but I can guess why AMD didn't want that.
Of course from a cost perspective a better option is probably the Phenom X3 8450e but it's going to be lower performing in most apps and from all I've seen power consumption isn't going to improve that much (at load obviously but performance per watt the X4 is likely to come out better most of the time). And since this is a reviewer platform, they wouldn't have cared so much about cost. The cheapest option is probably the 7750 and from what I've seen it should compete (in fact generally be better then) a E5200 but that has high power draw likely higher then the X4 you had and is not currently supported by the MSI Live DIVA bios.
So yeah while I agree with you you don't usually need a quad core for a HTPC unfortunately there's currently no great option on the CPU side given the limitations. Hopefully the Phenom II will help allieviate that (particularly the Athlon based Phenom IIs). Besides certain other review sites *cough* Anandtech *cough* seem convinced a quad core is necessary for transcoding (personally I've never seen the point but then again MPEG2 is common in your HDTV in the US)
Secondly you compared the audio output to a $4000 amp and nothing else
. For example when you say:
Our general reaction to the Maui PC amp was.... Wow! With the volume set at a fairly nominal living room level (peaks measured 80~85 dBA 1m from the center point between the two speakers), the change in the sound from the Linn preamp/amp was subtle. As with the Linn amps, the sound was lively, dynamic, detailed, clear, transparent. There were no obvious losses or degradations such as thinner bass or harsher sibilants. Mostly, the music came through much like before. It was quite impressive for a modest little $100 board inside a computer to come even close to matching $4,000 worth of discrete high quality audio amplifiers.
Perhaps all you are telling us is there is no reason why you needed a $4000 amp. This wouldn't surprise me since IMHO there are a lot of people paying for stuff in the audio world that makes little or no difference (e.g. 96khz/24bit). If you compared it to a say $300 amp (preferably double blind) and the Diva sounded a lot better then you can say something useful. Otherwise, it's easily possible all you're saying is that most people pay way too much for amps since they can't really tell the difference except at insane output levels they never use. Obviously if you didn't have a $300 amp this is a rather difficult proposition (borrow one perhaps?) but IMHO you should at least be careful with your conclusions. It's a bit like playing Quake 2 on an IGP and a 4870 which runs at 200++ FPS and saying 'wow the performance of a expensive GPU on a cheap motherboard' when in reality all your saying is no one can tell the difference between 200 FPS and 1000 FPS and Quake 2 is so old it's fine on any modern GPU.