Looking for a standalone workstation PC for a single user running heavy
database queries, likely Windows 32bit. Is it best to have a CPU with
plenty of cache or plenty of GHZ?

AMD X2 4800 with 2x1MB cache is double the price of X2 5000 2x512KB
cache. But would 1MB cache be much faster than 512KB cache?

Also would Intel be significantly better, usually Intel is a bit more
expensive.

The database system might not have much use for RAM beyond 2GB on
WindowsXP, but cache or Ghz?