Actually, the brand and model of the monitor is irrelevant. What the question to ask is "what is the main purpose of his computing?" If it is gaming, then you wil be looking for a monitor that is compatible with video cards using 64MB RAM or higher, although 32MB will work for most games. If he uses the computer mostly for Word Processing, Excel (or Spreadhseet), email and casual Internet useage, then 32MB video is fine. Programming in Visual Basic, 32MB or higher. Graphics, 128MB RAM and higher.
Fortunately, most models on today's market meet any of the above requirements, so your selection is huge. But again, the question is "what is the main purpose of his computing" then take it from there.