I think if the lowering spring is too stiff and the stock shockies will stuff up very fast, b/c I had experience of just changing lower,stiffer springs to my 98 V6 Camry 5MT, and the shocks do not absorb bumps properly now.
But I think IS 200 has much better shocks, so maybe it's ok, and 25mm should not do any harm to shocks.
SL