Digital Camera Flash Diffuser

Canon or Nikon or Other, Which Lens, Which Flash?
Right now these are the two setups I am looking at but I am open to any changes or any other opinions. My main uses for the camera are more skateboarding sports oriented pictures (outdoor and indoor), night city pictures and some portraits.
I am looking to spend about $1400 or less when all is said and done (shipping and whatnot included). All prices I acquired are from BHphotovideo.com. This will be my first DSLR and just trying to weigh out my options.
Canon EOS Digital Rebel XTi $520
Canon Zoom Wide Angle-Telephoto EF 28-135mm f/3.5-5.6 IS Image Stabilizer USM Autofocus Lens $400
Canon 430EX Speedlite E-TTL II Shoe-Mount Flash $240
(also 4gb cf card $60, flash diffuser $15, extra battery $50, glass filter $25) $1315
OR
Nikon D80 with Nikon 18-135mm f/3.5-5.6G ED-IF AF-S DX Zoom-Nikkor Lens with 2 2gb sd cards $1080
Nikon SB-600 Speedlight i-TTL Shoe Mount Flash $180
(extra battery $40, glass filter $15) $1330 Total
Here’s some photos for you to compare.
Nikon D80 with 18-135mm.
http://www.flickr.com/search/?cm=nikon%2Fd80&q=18-135mm+skateboarding&m=text
Canon Rebel XTi with 28-135mm.
http://www.flickr.com/search/?q=28-135mm+skateboarding&cm=canon%2Feos_digital_rebel_xti
Either camera will serve you well. Much of this depends upon how the camera “fits” your hands and your style.
Hope this is helpful.
Shoestring Studio Flash Diffuser