Maxtor drives might be a tiny bit faster and the noise level is still similar. I think the Seagate may be a tiny bit more quiet but the Maxtors are quiet as well. I mostly chose that in my spec for a cheap yet bad-ass DAW simply because New Egg doesn't have an 80 GB Seagate 8 MB 7200 RPM IDE drive availible right now, and going to SATA adds cost...
The XP mobiles are made for laptops but it's the same chip. Just doesn't have any hard set multipliers (although it will default to 6x if you don't manually set it in the bios) and the V-core at the rated speed is 1.45v. Basically they picked the best bartons and made them mobile since they would run stable at rated speed with less voltage. THis is what makes them so overclockable. 2400+ is probably the best bang for the buck and will still run 2400 MHz, although I'd probably recomend 2375 at 1.725v just to make sure the thing is drop dead stable. Mine is running at 2415 just fine though. Haven't tested it so see how far it will go but I didn't really want any headaches and or run the thing any higher than 1.725v. Bios health reports that my 1.725 setting is really only right around 1.7v though.
On my mainboard I didn't have a multiplier adjustment since it's an early Leadtek Nforce2, so I bought a rear window defogger repair kit at an auto parts store and did the pin mod trick to set the multiplier 12.5. (my older mainboard doesn't really like FSBs over 200) Since you are buying new, this won't be an issue as long as you make sure the mainboard supports multiplier adjustment in the bios. Most do at this point except the cehapest ones, and that super cheap Shuttle Nforce2 ultra gets good reviews for a no frills O/C Socket A board. Anther cheap overclocker is the ABIT NF7, and I've always had geat luck with various ASUS Nforce2 boards...