Computer requirements are determined by the types of imaging being done. 8K and 16K film recorders produce excellent output, but then an 8K image is around 120 meg, and a 16K can be over 400 meg. Buy as much processor speed as you can, but never at the expense of needed memory or adequate and fast storage. AV drives have noticeably higher sustained transfer rates over standard drives. RAID arrays can provide even more performance.
Tape is still the lowest cost solution, and is still the biggest pain to retrieve.
Mechanism costs are high, but optical provides low cost media. Consider solutions such as Iomega's 1 Gigabyte Jaz drive as an all-around solution. Fast speed, removable media may provide a single solution for archiving, short term storage, and day to day workspace. Garbage In, Garbage Out When determining the scanner or scanners you will need to meet your scanning requirements, be sure to select a scanner that is capable of capturing both the quantity and quality of information you will need. If your scans are lacking, you will be hard pressed to produce usable output.