Cartridge for a Rega P2

I'm looking for the least expensive cartridge to use with a planar 2 in a small room and a very modest set-up (NAD L40 and phono pre into Paradigm Atoms)- something that is still reasonably good with the thought of one day (when my kids are less destructive) of moving the table to the bigger room and upgrading at least the cartridge-
thanks in advance for the feedback-
Adam