So far, only company I've seen with images of the product. http://priuschat.com/forums/prius-m...sports-springs-now-available-04-09-prius.html
There are quite a few suspension improvements you can make, including the following (vendors are in parens; other vendors may sell them also): 1. Touring Edition front stabilizer/sway bar, rear stabilizer/sway bar, rear shocks, rear springs (Sigma and Toyota Parts places sell them). Note that the Touring Edition's front struts and springs are the same as those on the 2006-2009 Standard Prius. Note that the Touring Edition front stabilizer/sway bar is the only one that you can get now that's beefier than the one on your Standard Prius. 2. BT Tech front strut tower brace and rear stiffening plate (buy these at the PriusChat Store). 3. TRD Sportivo shocks and springs (Sigma and Toyota Parts places sell them). 4. Tom's braces - front strut tower brace, front lower suspension brace, lower body brace, floor strengthening brace (Sigma sells them). 5. Hotchkis, TRD and Progressive make beefed up rear stabilizer/sway bars for certain model years of the Corolla/Matrix/Vibe that will fit on the Prius (google search). 6. Other brand lowering and performance springs (Sigma sells them). Here's a link to Sigma Automotive Prius page -- scroll down to the end for performance suspension parts for the Prius: http://www.sigmaautomotive.com/jdm/prius/prius0405.php Almost all of these suspension parts have been discussed on PriusChat. Use the search function to find relevant posts and threads.
Xenthric, I don't know the answers. You might want to check out this thread, and PM the OP: http://priuschat.com/forums/prius-modifications/44779-blitz-springs.html
Eibach makes progressive springs which will lower the car as you mention and, since they are progressive, they will provide a smooth highway ride, but will stiffen up when pushed, will greatly reduce roll. Eibach provided the progressive springs for the Prius that holds the record in its class on the Bonneville salt flats. You will need to change the slow factory oil shocks for fast acting gas shocks, any good brand. Also get the Eibach front and rear alignment kits due to the lowering. Eibach is also much more reasonably priced, at $259.00 a set.