Well, because the FSB on the XP-M is 133MHz (PC2100) you could save a lot of money, buy faster RAM like PC3200 (200MHz), which means you don't have to worry about loosening timings or upping DIMM voltage until your FSB hits beyond 200MHz.(as a bonus this is ideal for a novice at this stuff; one less thing to worry about
The Abit NF7 motherboard is a very popular socket A board, I've handled it before, and I tend to agree with the the majority. Just keep in mind that all Socket A boards will be AGP based so don't go out buying a PCI-E video card.
Lower wattage is pretty much what you're looking for. Lower wattage leads to lower voltage getting pumped through your core which means that A)it'll run cooler to start and give you more temperature headroom to overclock into and B)you can increase the voltage a lot further because you have a larger gap meaning you can stabilize your CPU at higher clock speeds than most other CPUs.
Just remember that once the voltage is increased your temperature will start rising pretty fast so put some money aside for a good heatsink ($50?) so temperatures don't cap your overclocking.