I find this setting to help reduce jitter to create a blacker background. This setting blocks the other applications from accessing the DAC currently used by the audio player. For native 96kHz or higher files, I leave them at their native sample rate. If your DAC supports it, 176.4 is also a good setting to go for. When playing standard redbook material (16/44.1), I find that the most natural sound is achieved at either the 88.2 or 96 kHz sample rate (I’m personally leaning toward 88.2 as it gives me a weightier sound). Generally it’s good to have a higher bit depth (most high res files these days are available with 24 bit depth).
I find upsampling to yield more audible improvements over 16 vs 24 Bit word depth. Unfortunately if you’re on the latest OSX (Lion), Integer mode is no longer supported. However, not all DACs support Integer mode and so it would depend on the particular DAC that you’re using. Integer mode is the expressway and we all love the expressway. You can take the expressway/toll road, or you can take the country road. Think of this concept like when you’re driving to go somewhere. Integer mode creates a shorter path from the audio playback buffer to the DAC. The size of the buffer also depends on how big are the files you’re playing, as some really big 24/192 files can go up to 100MB in size. Personally I find the stock 256Mb settings to be just fine and I don’t hear any audible benefit in increasing the buffer. Obviously a bigger buffer size is nice but it would also depend on how much RAM your computer has because other applications like your email reader, browser, itunes, twitter client and so on also needs RAM to run on. The Buffer size setting tells the player how big of a memory you want to allocate for your audiophile player.
On regular players, playback is achieved by continuously reading the hard disk and sending the data over to OS X for playback. Playing the data over a memory buffer has the advantages of reducing potential sources for jitter such as the CPU overhead required for hard disk streaming, the actual reading process from a mechanical hard disk (this is not an issue with SSD drives), transmission over cables, and RFI issues. This feature gives you the option to load the digital files into a memory buffer (RAM) before being processed by OS X for playback over to the DAC. They may have different labels, but in essence they do the same thing. There are a few common parameters offered by the different players.