As far as shocks go. I had YFZ fronts on my rappy for a bit (found a deal on a-arms / shocks about 3 months later) but the time I DID have them on it was a NIGHT and DAY difference. so much smoother.
for the price, its a solid mod.
As far as single vs. duals.
There's a SOLID gain when comparing the 2 to make the cost worth while. If there's ANY doubt in your mind that you'll upgrade the motor in the future. Its best to get it out of the way.
I had my stock pipe for 4 months.
bought an HMF full pipe setup.. Had that for about 6 months. And sold it and bought barker duals. Haven't looked back since.