When I used to use my B&W regularly I dropped a 80GB Seagate Barracuda 7200.10 PATA drive in it with 8MB cache and it made a whole world of difference to the speed. Although PATA is nasty, having an onboard drive that's capable of even just matching the 33MB/s transfer rate of the ATA33 bus (which the original Maxtor and Quantum disks are not, by a mile) will greatly benefit the machine. If you are planning to get something for the longer haul, Id probably go with a PCI SATA card instead of SCSI as it's less expensive overall and you can more easily utilize new parts rather than used ones (most second hand SCSI drives are ex-server or ex-workstation and have been run into the ground). If you want the maximum benefit from SATA you need a 64-bit wide PCI card. These are available from a couple of Mac vendors but are expensive. 32-bit wide PCI cards will work just fine but you'll find you get a bit of a bottleneck on transfer speeds over a 33MHz 32-bit bus if you use more than one disk at once. This is partly due to the slow bus and partly the fault of the rather lame PCI bus design in the B&W. SATA also conveniently bypasses the awkward Rev 1 ROM/IDE issue.
RAM and CPU upgrades always help, whatever you fit. Mine is running a 500MHz/1MB G4/500 much like Macster's beige and it fairly whips along. I run Tiger quite happily on it with 768MB RAM. One major thing that makes it so good is the graphics card though. I use a Radeon 9200 PCI(66) Mac Edition card with 128MB DDR2 VRAM. It's not up to AGP speeds bus-wise but it will pretty comfortably out-perform something like a GeForce 2/4 MX in Mac OS X, purely because it has a ton more VRAM and the GPU is better.
For nice extras consider a decent FireWire card, as the onboard bus can't hack having 2 devices at once on it, and I believe Rev 1 machines are prone to very occasional data glitches. Also consider a good NEC-based USB 2.0 card. Remember though loading up the PCI bus with extra throughput will slow it down significantly. if you get them all talking at once. Realistically if you want external storage you would be better getting a SATA card with 2 extra E-SATA headers on and using that. That will load the SATA bus down a little but it will at least keep the cross-talk on the PCI bus to a minimum.
Hope that all helps
RAM and CPU upgrades always help, whatever you fit. Mine is running a 500MHz/1MB G4/500 much like Macster's beige and it fairly whips along. I run Tiger quite happily on it with 768MB RAM. One major thing that makes it so good is the graphics card though. I use a Radeon 9200 PCI(66) Mac Edition card with 128MB DDR2 VRAM. It's not up to AGP speeds bus-wise but it will pretty comfortably out-perform something like a GeForce 2/4 MX in Mac OS X, purely because it has a ton more VRAM and the GPU is better.
For nice extras consider a decent FireWire card, as the onboard bus can't hack having 2 devices at once on it, and I believe Rev 1 machines are prone to very occasional data glitches. Also consider a good NEC-based USB 2.0 card. Remember though loading up the PCI bus with extra throughput will slow it down significantly. if you get them all talking at once. Realistically if you want external storage you would be better getting a SATA card with 2 extra E-SATA headers on and using that. That will load the SATA bus down a little but it will at least keep the cross-talk on the PCI bus to a minimum.
Hope that all helps