Pax Anglia,
I have always had SCSI-based machines, currently using very staid 233Mhz Pentium with Fast SCSI-2 devices (HDD, CD-ROM, Jaz backup drive etc) and will go ultra-fast ultra-wide SCSI on the next machine. This works well on Windows and Linux. Modem is USRobotics Courier Dual Standard, works very well. SCSI is fast!
Current machine actually doing rather nicely so not in hurry to upgrade. Only problem with SCSI is initial expense of hardware but very fast and usually no problems with conflicts between hardware.
Suggest 256Mb RAM for your machine, and AGP video card with 64Mb RAM, more if available.
As for remaining bits, get the best your wallet can afford and definitely stick to well-known name brands. Generics are a pain in the b*tt! (R O Tiree gives sound advice!)
Suggest get 15" wide printer...you can always put narrow paper in it but you can't put wide paper in a narrow printer!