If you want to go lower and spend as little as possible, get AEG Custom springs.
going 60 - 70mm lower won't be legal so no need to worry about that.
You can get coilover suspension with your budget, just don't bother asking about performance, quality or reliability.
If I were you, I would save for quality. because been there done that.
Your shocks will die in 6 months with springs that low