I wish there were better options for suspension state side, but the primary problem with road racing style suspension is that its just too fragile for rallying. A good example of this would be to look at Ohlin's offerings for the Mitsubishi Evo. The road race stuff is tiny compared to the heavy duty stuff, the TTX/TPX combo.
Budget for the suspension would be a nonadjustable kit from JVL, a guy in the PNW who puts together kits based on Bilstein 45 or 55mm shocks. Prices are usually about $2000 for a set.
High end for this build would be the Proflex dampers that are used on some of the CM3C cars that see gravel. These retail for ~4900 euros at the moment. These are my first choice, but I'm not sure I'll be able to dig up the coin to make these happen.
Rally suspension is a funny thing IMO. Until I got to ride in a car with proper gravel dampers, I was wondering WTF people were spending $5k+ on suspension. After my ride-along, I understood. Its flat out amazing what you can do to a car with this type of suspension. Crazy off angle jump 5 feet off the ground...no problem.
Try that on regular dampers and you'll blow them out on the landing.
Couple videos of my Evo doing work:
Towards the end of this one, we're doing ~120mph catching pretty good air:
http://www.youtube.com/watch?v=TzanQzyX4xk About 2/3rds of the way thru this one, we go pas a dump truck, and the road just after that is enough to shake apart our truck, but motoring over it with the rally suspension, my wife remarked "that suspension really proved its $$ worth today."
http://www.youtube.com/watch?v=UNJU_lJqd40 BTW, I do have a buddy who works at RRT, so I will certainly be asking about the AST stuff before I pull the trigger on something. The key for rallying is to get rid of that inboard spring in the rear suspension and convert it to a full coilover setup.
Dave