You may get better responses from the hobbyist's that frequent diyaudio.com and diymobileaudio.com.
I did it awhile back (probably dating myself). Dropped a Clarion coax into a self-made box, and the results were "meh".
Are you using the included crossover? They are typically designed for car installations where the woofer and tweeter are further apart. The woofers are normally optimized for free-air/infinite baffle applications, and you'll need a box of suitable size. Not to mention the box you build (or get pre-made) needs to be of sufficient quality to ensure nice, inert home for your comps.
I'd think what you build would be better than a $50 pair of bookshelf speaks, but depending on the time your want to invest will determine how good it ultimately is.