Which Is Better Uk Or American Built Cars.

You need new shocks
Get stronger aftermarket shocks and it might work for a while, get stiffer springs and it will work for a longer time

There are two types for that chassis.  SE/V6 and 4 cyl specified . . .   Your best bet is to go with bilsteins.  They will outlast the vehicle and its laced with precised valving.  A set of 4 should cost you about $200.  They are called Bilstein Touring and its a lifetime warranty.  OEM is too expensive and isn't lifetime. 

I don't think it is a good idea for a used set of shocks.  You don't need springs (except your condition is extreme).  Springs are lifetime. 

Never alter the height of your vehicle.  People on the other hand would recommend you drop the height of the vehicle (which in this case is what you are avoiding).  The good news for you is that Bilsteins will raise the height of your vehicle by about 1/2 an inch.  Don't worry about terrain surfaces, it's designed for all kinds for it as well.

When you ask for Bilstein, be sure to categorise it.  They are 4 in catgories.  The only version for your Toyota is the Touring Class-twin tube.  You need to get help for the part number (would start from tc*****).  I recommend to purchase it online and have it shipped.  It is free shipping via UPS and keep the receipt.  If anything goes wrong (wears out or becomes flat), you'd have it replaced.  They claim its engineered to outlive your vehicle.

It's the best value for your money.  Believe, ride quality and handling will change dramatically from the stock you have.  It might be best option to also change the spring seat and maybe strut mount if they look weak or bad.  The subframe should be replaced.

Go to the bilstein site.