Any mods that improve ride quality?

My .02

Start small and work your way up. I would go with, as mentioned before, adjustable shocks like Tokico D-Specs and some softer springs. This way you can adjust how soft or stiff you want your ride. This setup is perfect if you like to occasionally open track the car or auto-x it. You'll lose some grip but unless your seriously Road Racing or Auto-Xing the car I don't think you'll notice any adhesion difference. Probably more important than suspension, if adhesion is an issue for you, is stickier tires.

If that doesn't satisfy your bum than you can go to the next level and go IRS.

John