I know coilovers are better than springs for the most part, but is there any brand(s) that make springs that could work well with stock struts without them blowing out easily? I heard tanabe is pretty good.. main goal is to get springs only, for now atleast..
What look are you trying to achieve and how low are you trying to go? Depending on your goals, it may be cheaper in the long run to just keep the money you'd put towards the springs and just wait longer to save up for coils.
I can't comment on how Lexus vehicles work with springs, as I've only owned coilovers on my GS. However I will say this from past experience: lowering it by that much on stock struts will have them wear pretty quickly. Also, you should take into account the age of your car and how many miles are on it. The more "seasoned" the vehicle, the quicker the stock struts will fail.