Considering your shocks only have 50K miles they're probably in good shape. You could probably go for awhile without shocks. A 1.5" drop is not so low that you will be bottoming out all the time. Granted the ride will be a tad bit more bumpy.

I say you put the springs on and when you have more money upgrade the shocks if they start going bad. Unless you autoX or roadrace I would recommend just waiting to do both at the same time.