1. If you are set on the board, but need to go with stock speeds and cooling get the mobile 2600+. Good performance for now and overclockable later.
2. If you have or can get better cooling, go for the mobile 2500+ and overclockk it. I think some speeze coolers or the tr2-m2 would do it for 12-17 bucks shipped, which is partially offset by the savings on the 2500+.
3. RAM is not going to hurt you too bad because you are used to it. There is a deal on kingston 512 PC3200 CAS3 for 55 shipped after rebate at outpost
link I got some mushkin C2.5 from newegg, today they have corsair vs C2.5 for a couple bucks off $77
#2 is by far what I would do. The price-perf declines slightly from there and since you have the NF7-S version 2 you can peg it up to 2.2GH easlily! May need thermal grease such as AS5 or ceramique or shinetsu or ?
Both #1 and #2: The default bus speed will match your current ram 1:1 and when you upgrade cooling and memory, you can go into the BIOS and up the fsb to match.
EDIT: When you overclock you can adjust the fsb/ram ratio to fit whatever if you don't/can't oc your ram There is also a decent chance you could overclock your current memory if it's a good brand or if you relax your timings and maybe up the voltage a tad if it needs it (more BIOS stuff) Worth a try for sure. That would mean running at 1:1 200MHz FSB and probably the multiplier of 11 so your result would be around 2.2 GHz. which is the speed of a 3400+ chip. Look up what vcore you need in the
mobile OC thread or experiment. Should be around 1.575V? I forget.