Corsair XMS runs at ridiculous latencies. Try for an active precharge delay of 5, ras to cas and precharge delays of 3 and cas latency of 2t.
If you can't run XMS at those speeds, you got very unlucky. As for what they mean, I really don't know. All I know is that 5 3 3 2T is pretty much the pinnacle of memory timings.
I just got a Barton 2500+ myself a few weeks ago. I've got it running at 2.32 Ghz (11x211), a 24% overclock using an ThermalRight SLK700 with a basic 80mm fan. Your chip will almost certainly be locked, so multiplier OCing is not an option unless you like filling in the pits between bridges to avoid the grounded base.
How far you'll get with your FSB depends almost entirely on cooling. Your CPU and Northbridge cooling solutions particularly. I know your XMS will have heatspreaders, so it's unlikely they'll be your bottleneck.
For my overclock, I booted at stock speeds to get all updated drivers for my entire system. Then I went about overclocking. I started by setting the FSB to 210 and setting the DRAM ratio to 100%. The RAM is XMS PC2700 by the way. I booted, ran Sandra's Burn-In Wizard using only the CPU arithmetic test 25 times. 210 passed with flying colors. Next I jumped to 215, which booted, ran, but only half the time makes it through the burn-in. So I throttled back, and 211 is where I'm happy. 100% stable and max processor temps of 44C after 3 hours of full load.
All of this is at stock voltage of 1.65V.
Where you're going to be limited is your cooling solution. Obviously I could get higher with water or more exotic forms of cooling, but I'm strapped for cash. As it is, I'm running faster than all but the newest processors for about 1/6th the cost. Heatsink cost me $30, $8 fan, lost of case fans to keep ambient low. Unless you don't have a cooling solution at all, you'll be able to run at 3200+ speeds no problem, at stock voltage. That's why I love the 2500+