are the springs you got from traxxas? if so purple is not 17lb/in, its 36.5lb/in the stiffest available!
if you have the 36.5lb/in purple springs they are going to be crazy stiff and you'd need pink fronts. i have the silver front and blue rear and with 55wt shock oil its already very stiff.
oh, and keep the p2's they work with any springs and are better then the stock p1's.
check out the chart in the link, also where do you plan on running this thing, bashing only?
shock oil seems to make a very big difference as well, my 55wt is a huge difference compared to stock. i can drop the truck from 3 ft and it won't bottom out. to me this means its ready for the big jumps.
also, if i were you, i'd go to the traxxas forums, more help available, just read up on the first few pages and faq sections.
http://monster.traxxas.com/forumdisplay.php?s=&forumid=55
so it really depends where you springs are from. if they are traxxas then its 36.5lb/in for purple which is the stiffest offered. i'd probably go atleast 55-60wt shock oil if you decide on the purple/pink combo.