I'd say all 3 major companies, PST, Prothane, and Energy Suspension make complete kits, and are similarly priced.
If you're building a street kit, you may consider calling Maximum Motorsports and talking to them about your goals, and see what they reccomend. Urethane isn't always the solution, as many, many quick cars out there are using rubber bushings in their control arms and such.
just a thought.