First off, we want to congratulate AMD, Nvidia, and Intel for upping the ante over the past year and delivering some really useful hardware and software able to handle HD playback. Only a short while ago it seems that HD playback on an integrated IGP was a tradeoff at best and horrendously buggy at worst. This time around, things went so much more smoothly that we feel comfortable saying that Blu-ray playback with an IGP is viable, which is no small accomplishment. It certainly doesn't hurt that modern-day budget CPUs are worlds ahead of where they were a year ago.
With that out of the way, where do we begin? Let's start with a look at the GeForce 8200. While it's a competent platform, it's a dismal choice on which to base the purchase of a Blu-ray-equipped HTPC. Basic 1080p playback is viable, but don't ask the chipset to perform good noise reduction or it will stutter terribly. Indeed, if you choose an AMD CPU for your HTPC, the Radeon HD 3200/3300/4200 IGPs are the only real choice if video quality is a concern. The GeForce 8200's only appealing factor is its relatively low-power usage in comparison.
That brings us down to six contenders: the 780G/790GX/785G, the GeForce 9300/9400, and the intel G45. We can further discriminate with the question: how serious are you about home-theater audio? If you are an audiophile, you should know that out of these remaining options, only the GeForce 9300/9400 can handle uncompressed eight-channel LPCM audio over HDMI 1.3. This means that if were hoping to use PowerDVD to decode Dolby TrueHD or DTS-HD MA and send the LPCM to your receiver, then the 780G/790GX/785G family of IGPs aren't for you.
But before discounting them completely, we will say this: the 780G/790GX/785G IGPs can easily handle six-channel DD/DTS audio, and if you were planning on using a card like Asus' Xonar HDAV 1.3 anyway to bitstream those high-def formats, then this shouldn't be an issue for you. Once you consider this and take into account that 780G motherboards start at $60, which is about $40 less than their 785G and GeForce 9300 counterparts and almost enough to pay for a CPU, the 780G becomes a very attractive option. Perhaps it's the ideal choice for those of us who aren't serious enough about their home theater audio to upgrade our amps specifically to play back the latest audio formats.
However, if you do want the flexibility of eight-channel LPCM and the best integrated video quality possible, then you have to choose the GeForce 9300/9400 or Intel G45. Just pay attention to the driver you're installing and PowerDVD's hardware de-interlacing settings, respectively.
Either way, I can say without hesitation that if you choose the 780G/790GX/785G, GeForce 9300/9400, or Intel G45 IGPs for home-theater use, then you won't be disappointed.
On a final note, I would be remiss to avoid pointing out that any motherboard with a PCIe slot can be transformed into an HTPC powerhouse with the addition of an inexpensive discrete graphics card like the Radeon HD 4650. If you're looking for more than just HD video playback (the occasional game at 720p, perhaps) then the discrete route is well worth the extra money spent.