As to the buffer, remember this drive is Ultra DMA 33 compliant, so it will run as fast or faster than many of our first hard drives. From what I have seen, this drive doesn't need a huge buffer since the data throughput is fast and even, thereby utilizing drive resources very well. This is of course my 0.02, but I am happy with my drive and I said I would never have another DVD-ROM after the Que/Samsung mistake I purchased a few years ago.
As to PowerDVD, under Config it does have a tab to purchase the Audio Packs, so if you are expecting it to come with all the surround sound modes it apparently will not. This is not a big deal for me, as I live in an apartment and it would be over-kill but if you invested in the latest 5.1 card and speaker system I would imagine you would want the full effect.