I imagine that when you are talking about a 2.8, you are referring to an AMD Athlon XP 2800+ since your motherboard supports Socket A chips.
There are many 3200+ AMD chips: ClawHammer, Venice, and Winchester. These processors use either the Socket 754 or the Socket 939. Since your board supports only Socket A chips, you cannot use any of those listed chips. If you want to upgrad to one of those chips, you will need to upgrade your motherboard. If you upgrade your motherboard, you will most likely also want to upgrade your RAM to take full advantage of the increased speed of the system bus and processor.
What is the problem that you are experiencing that causes you to want to upgrade your system?