You didn't mention what temp your cpu is running at with 1.85v. If it's going over 50* C, I personally wouldn't let it run at that voltage. Leave memory timings set to "normal" while finding the limits of the cpu, then work on memory timings.
First, I would see if it will run fully stable at 138 fsb (~1725 MHz) with default voltage. If it won't, you probably won't get it to run stable at 1900 MHz with less than 1.9v - and that will make a LOT of heat. You'll need one of the best coolers available.
Your best bet, regardless of how fast the cpu will run, is to unlock it so that you can run the fsb at 166 or higher. I unlocked my 2100+ using White-Out and conductive paint from a Permatex window defogger repair kit (~$9). The trick to using White-Out is to barely cover the bridge contacts on the cpu with clear tape, and fix the ends of the tape strips so that they can be removed VERY quickly after applying White-Out in the gap. Inspect it carefully with a strong magnifier before proceeding to the taping/painting of the bridges. If you don't like the way it looks, rub it off with a toothpick and redo it. I didn't seal one of the pits on my first try, and I ended up with only 5, 7, 9, and 11 multipliers. I masked and painted one bridge at a time, and let each dry for about five minutes before putting tape over it to do the next bridge. If it bleeds a little under the tape, joining two of the bridges, let the paint dry for a while, then cover the part you want to stay intact with tape, then rub a pin or needle point to remove the unwanted paint - it becomes brittle and scrapes off easily. Patience and a good magnifier are necessities.
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