You could use the zeos low level api interface, without installing comps.
It's also crossplatform.
You only have to add
{$IFDEF FPC}
{$MODE OBJFPC}{$H+} // or {$MODE DELPHI}
{$ENDIF}
FPC also supports macros that are verry useful for calling convention tricks.
I'm not currently using PostgreSQL because i have to run the server on 9x machines.
I might need it in the future, but for now FireBird is smart enough, light and works also on 9x and many other platforms.
I know version 8 is really powerful, but if you stick to SQL and do not need all the API funcs then maybe older interfaces also work.