Interesting articles regarding water cooling and ducting air to the CPU at
Also searched Google for:
AMD 2500 barton temp range
And found a few threads (first two screens) that claimed success at lowering temps from the levels you quoted you are running.
My own experience is with a 2.8 P4 and may not be as important as those with your own processor.
Had to remove an Abit IS7 MB to return it. Replaced with an Asus P4P800 Deluxe. Only other change was removing the Intel Thermal Pad and using Arctic Silver III with the same stock Intel Heatsink and fan. CPU temps went from 45-50 C down to 34-39C. The Arctic Silver literature states you should expect 2 degrees or more improvement after 200 hours of operation. Looking forward to that.