It's probably not something you want to do because it's closer to daytrading than mining, but buying stocks from other mining contracts ("PMBs") when they are blatantly undervalued and selling them when they are more attractive, while taking the PPS mining profits in between is something that has proved to be a valuable short/mid-term investment strategy as far as I'm concerned.

As for hardware purchase, I would hold the funds until September. We are in uncertain territory right now.