I think that's the problem though - you are never going to get anything that good from something built onto a PC motherboard, for all kinds of reasons.
I think you are right to have concerns, but don't be too prejudicial. If you open up many A/V receivers these what you will see inside looks a lot like a PC, sometimes even with various components on daughter boards. The use of switching PSU is becoming very common, especial in conjunction with Call D amplifiers (which themselves are becoming more common at the upmarket, like Pioneer's top of the line stuff using ICEpower).
In particular, it will be very hard to come up with a design that gives plenty of noise isolation, does not generate too much heat and provides enough power to run a sub, or even larger woofers reasonably.
Using unpowered subs is a pretty esoteric application! Even for your point to woofers, it is all a question of speaker efficiency. If you've got 90 dB @ 1m or better, how much power do you really need at TV viewing distance, 10W/channel? This amp is rated at a combined 100W, so I think it can get the job done for a typical home theater setup. I'd have more concerns about large room music listening, but that is not the target application for this product.
There is a reason amplifiers, particularly multi-channel ones, are that big.
The real reason is marketing. High end manufacturers purposefully make their stuff big and heavy because those attributes actually score them points on reviews, as the old school line of thought is that size and weight = quality. My Class D from Harman Kardon is gigantic for no good reason other than it would have been hard for them to have a $1500 list price on a 20lb receiver. I think things might be starting to change though. Rotel has a $2500 7 channel ICEpower amp that is the size of a DVD player and only weighs ~ 10lbs. On the other hand, Pioneer's new ICEpower receivers are still gigantic and weight 50lbs or more . . .
Another issue is inputs. Presumably everything is PC controlled via the soundcard, so no remote control access while the PC is turned off and no pass-through or input selection for things like games consoles, if you care about that kind of thing.
I agree 100%. This is the big issue to me and why I see little point in an HTPC with a built in amplifier. On the other hand, I've only got one TV. If I had a second room where I also wanted an HTPC, then this might be a very compelling product for that scenario. Things would be better all around if cable/satellite companies would allow DCAS or similar software solutions to allow PCs full cable box functionality.
Finally, if you want a 5.1 system you will probably want quite a bit of processing when listening to stereo sound, and probably even when using 5.1. From the looks of it the processing options in this system are not as good as on a good dedicated receiver.
I disagree here. When I listen to music on my 5.1 setup I listen to it in unadulterated stereo. Anyway, I'm pretty sure that with all the Direct Show filters available, processing options on the PC demolish those available on A/V receivers.
To be honest, even if you don't want a full size receiver or amp, a little T-amp would probably be a much better bet for stereo sound. That's what I'd suggest for listening to music. For movies where you probably want a sub, there are some good powered 2.1 systems in the Â£100-150 range.
What reason is there to believe this wouldn't be as good as a T-Amp? You know the currently produced version of the T-Amp is a PCI card just like the one that comes with this system (except that it is just 2 channel and rated for a lot less power), right? With the right speakers, I'm sure this could compete with any powered 2.1 system, but it would likely be no cheaper, as good speakers do cost money.