150 watt metal halide?

I recently purchased a sun systems enclosed ballast 150 watt hps. at my local hydro store the guy asked if i was having wispy buds. i havent done a grow with it yet, but just assumed it was a good light. he recomended i get at least a 400 watt switchable that he offers for $200, and by the convertable bulb for the setup i already have for vegging, so i dont waste the money i spent on the sun systems. i guess my question is what route should i go with a limited budget. any help would be greatly appreciated.