Now you've done it, this is a hobby that can take up most of your disposable income and free time [smash]
Opinions will vary greatly here, but I say it's up to you whether to keep everything Colt or mix and match, this goes beyond the stock to include everything else.
You should find a Colt stock and try it, then get the new ribbed unit and give that a spin before buying either. I've had the fiber glass, aluminum and the new model, I like the new one much better, it's a little longer, has a larger and slightly angled butt end and a sling loop where the fix stock's loop is, wheras the original telescopic stock has a slot like longitudinal "loop" at the rear top, it's probably an afterthought. Unlike the aluminum stock, it won't rattle. But if you want to put a rubber butt pad or cheek rest, they don't make any for the new model yet.
Bushmaster sells both the new ribbed 4 posiiton model, and the imporved 6 position "original style". [url]bushmaster.com/shopping/buttstocks/[/url]