mono/henotheism

Mrpastasmissus is getting rather worried by my recent posts. He's been worried before when I've been writing essays on various heresies. Probably understandably when I come out with things like "When you see where Arius/ Nestorius was coming from, what they said is actually quite reasonable"...
So we got into a discussion about what the Bible says about the existence or not of other gods. I'm not sure if it's simply an issue over terminology. What I actually believe is in one God who is a tripartite unity who is the cause and ultimate end of everything. I also believe other spiritual realities exist - created beings and less than God - angels and demons being the standard terminology, but also known as principalities and powers etc. (MrPM is quite happy with this :-))
So when God refers to "other gods" I take it he is referring to these other spiritual realities, as well as to anything we might choose to put in God's place.
Can you apply the label "gods" to such spiritual relities, or is that just misleading? Can you draw a distinction between "God" and "gods"? Does referring to them as "gods" turn me into a henotheist?

monotheism

Rather a long gap in writing here, partly due to working extra shifts to cover for a colleague being off sick. I've also been trying to process quite alot of thoughts that have come up following some of Jarred's comments.
So, here goes with the latest one...
Christianity is a monotheistic religion. I'd always thought that meant believing that only one God exists. But rereading the Bible suggests that other gods DO in fact exist. Maybe I'm more used to hearing them referred to as "principalities and powers" - in other words, some kind of spiritual entities that aren't as powerful as God.
So does being monotheistic mean believing in one ultimate God, or does it mean worshipping only one God?