It's been running on water for the last week or so. I did have to buy the current 6800 style "hat" for the MAZE4. This uses the four point mounting system and it is a perfect fit on the X1900. I used aluminum heat sinks for the RAM.
The results? MUCH better! Needless to say, that fan on the card was WAY louder than I liked. Now, it never gets above 39C under full load (fully overclocked). Before, it was pushing up towards 70C.
Stock, the best the ATI overclock utility would give me was 630 Mhz (yes, just BARELY above stock!) on the GPU and about 750 Mhz on the RAM. On water, the GPU is maxed out at 690 Mhz (most the ATI CCC will overclock it) and the memory is also maxed out at 800 Mhz. I have a feeling it has a lot more room in it once I get better RAM sinks and use an aftermarket OC tool. As it is, I am very happy with it's performance. Definitely worth moving it to water cooling.
Oh. And the card looks absolutely tiny with just that water block installed! That factory cooler is HUGE!