I find that most spices must be slow roasted and stirring occasionally to "wake them up." Meaning that applying a little heat allows the essential oils inside the spice(s) to maximize their potency.
In you situation, try slow roasting your whole coriander seeds and then use any grinder. I use the Magic Bullet with the horizontal blade and not the one with 4 blades (this is for grinding wet mixtures). If you want even finer, you can sieve these through a steel mesh. The ones that were filtered, put them back into your grinder and repeat if necessary.
As for cardamom, I use the entirety in my spice blends. If a recipe does call the seeds to be removed (as in: use only the seeds), slightly bruise (crush) with a knife so that you can pull the husk (skin). Do NOT discard the skins! If you have loose black tea, add those green cardamom skins into them. They impart little bits of cardamom smells to the black tea.
Certain spices don't grind well, e.g. dried vetiver roots. It is then not only do I grind first using the Magic Bullet, I then have to filter them, further grind in heavy mortar-pestle, and repeat if necessary. Dried galangal (both the greater and lesser) are hard. Grinding and mortar-pestle is a must.
