Forget chili powder – the trick is using a mix of dried chiles, choosing from 3 or 4 types. Keep notes, and try different mixes to see what you really like. You can’t go wrong though.
The chiles from the “mild” list bring great flavor but not much heat. A can of chipotles in adobo adds some heat (and super flavor) but for real heat include some of the hotter chiles in the mix. Just don’t go crazy unless you’re certain your audience wants it.
To find a variety of dried chiles you may need a specialty grocer, or fire up the intarwebs. Some mainstream grocery stores carry only one or two types — and you should check the expiration date.
Here is a list of dried chilis, sorted roughly by heat level — with links to buy them online. This is not a sponsored product placement, just a convenience. I have no relationship with these sources and don’t vouch for them. I buy my peppers at a local hispanic specialty market (also a great place to get your chorizo!)