Err what's the RAM timing now? 5-5-5-15 is conservative, but RAM tweaks should be done last. Pump FSB to your target first.

Anyways, your target is 3.2Ghz right? Target FSB then = 356Mhz.

Section A: ~3.1Ghz
1. Go to FSB 345, leave all voltage settings for the moment.
2. Use IBT (Intel Burn Test, it's faster and more accurate) 10 runs.
3a. If pass, good, go to section B.
3b. If fail, bump Vcore one notch, retest.
4a. If pass, go to section B.
4b. If fail, bump Vtt and Vnb one notch, then retest.
5. If pass, go to section B. If anytime fail, repeat steps 3 and 4 (bumping Vcore and Vtt/Vnb 1 notch at a time) until stable.
6. Take into account temperatures. You're on stock cooling, so it might get out of control. If load >70C, stop increasing FSB, that's your max without an improved cooler.

Section B: FSB356
1. Once you have a stable system from Section A, reaccess your BIOS and pump FSB to 356 = 3.2Ghz.
2. Run IBT 10 loops, if pass, Section C.
3. If fail, as above increase Vcore and Vtt/Vnb until stable. Shouldn't take much, but be careful of temps.

Section C: RAM - DDR2-890
1. Once your system is stable at 3.2Ghz, it's time to play with the RAM. FSB356 will give you DDR2-702. If you want more performance, bump Vdimm to 2.0 like you said and set memory divider 4:5.
2. This will result in DDR2-890, which your RAM should be ok with. Run memtest: http://www.memtest86.com/
3. If pass, good, now set timings 5-5-5-12 and run memtest again.
4. If fail, sorry your RAM cannot take it. Back to 1:1, set timings 5-5-512 and run memtest.

At the end, you'll hopefully have a stable 3.2Ghz system =)