As far as graphics boards go, most systems don't really care what kind of board you have as long as it supports overlays. There are some exceptions to this rule however. Matrox systems prefer to work with particular boards (and are happiest with Matrox graphics boards - surprise, surprise). The ADS PYROProDV doesn't like TNT2 boards, Pinnacle doesn't like Voodoo 1 or 2 boards, and no one seems to like Elsa boards. The amount of memory on the graphics card is another area where most capture boards don't really care, but again, some capture systems prefer cards with at least 16 MB. The graphics board usually comes into play during editing and displaying transition effects but is cut out of the loop during capture.
Pinnacle's DV500 Plus takes advantage of the new audio mixing features of Premiere 6.
Most video system VARs who are honest will tell you to get the cheapest audio board you can find and some will even tell you to remove it during capture. There is one caveat here, audio boards are notorious for eating IRQs, stealing cycles, hogging busses, and crossing memory boundaries so if you start running into problems with your capture system try disabling the audio card first. Most capture systems don't need a separate audio capture card and DV-based systems can capture both the video and audio from the same stream over IEEE 1394 so removing any audio cards is actually a good thing.
A good monitor is a must when working with video and I strongly recommend getting and using a video calibration program such as Displaymate Video Edition from Sonera Technologies. (I'll warn you now. Most people don't know what to look for when adjusting a monitor and are perfectly happy with what they have. You may even find that a properly calibrated monitor looks 'funny' or too dark. Displaymate can help you properly calibrate any monitor but it can also reveal problems that can't be fixed and from then on you'll be seeing them every time you boot up.)
I would not recommend using LCD displays since colors shift drastically depending on your viewing angle and their color reproduction isn't as good as a CRT. LCDs are great for CAD and most other applications but they just don't cut it for serious video work. You can use them if you have to but what you see on your screen may or may not be what everyone else will see when they look at your videos on a TV set or on their monitors. That's the reason you never see LCDs in professional video post houses or broadcast stations.