First off, does crucial make pc2700 DDR? I believe corsair or mushkin (or both) sell pc2700. Also, stay away from OCZ as I've heard many bad things from them. Also, try your hardest to get 512. Although prices are high, they most likely won't drop in a while. Maybe get a non-raid version of the motherboard to compensate a little bit for the price of the extra 256.
Also, I would strongly suggest against the IBM hard drives. They are known to fail, not so much the 60gxp but they are still known to fail higher than average. Although they are fast, their technology to make it that fast also causes many failures in the hard drives. I suggest Maxtor (you'll have the ata133 option as well) or Western Digital. Seagate is very good for noise too.
Also, for the power supply, don't get any PSU that's around 400w. Make sure it's a quality PSU. You're better off with a good 300w than a generic 400w.
EDIT: Also, good luck and enjoy your first built PC!!!!!!