for springs i think anywhere from 125-220, youll want to get shocks with the springs otherwise the stock shocks will blow out. install depends, i did mine (free), but a gas station w/a shop in the back told me theyd install them for 50 bucks with the shocks/springs.

for my catback i have a Apexi World Sport. great quality and sound. not loud, but its there, and just wails in VTEC.
other brands

Greddy - good stuff, have heard some rust and scraping issues.
DC - TCS is full stainless steel, and not loud at all.
5Zigen - makes the Fireball, canister style, pretty loud, good quality
Spoon - N1, axle back muffler, suppose to be damn loud, expensive, pricey
Mugen - Twinloop good quality and quiet, pricey
HKS - good company, havent heard any on a honda though
Comptech - full stainless steel, damn good quality, quiet pricey