I take smaller doses of harmalas with melatonin before bed pretty consistently. I never have any trouble getting to sleep or staying asleep with this combination. I tend to sleep (or want to sleep) a little longer than if I just take melatonin alone or don't supplement anything before bed and I dream vividly but still wake up feeling rested and refreshed. If you'll indulge me, I'll try and elaborate a theory I've developed about this.
I think you may be on the right track with the catecholamines. I don't think loading up on pharmaceuticals is the answer here however. It would be safe to say that in a very generalized way MAOI's are going to enhance the effects of your current biochemical balance. There are a whole lot of things effecting this, but in the interest of simplicity of explanation let's just discuss the one that is most pertinent to this issue.
The brain functions on what is known as the sleep-wake cycle, which consists of circadian rhythms and sleep-wake homeostasis. Very basically your brain runs a different cocktail of chemicals for wakefulness and for sleeping. One of the major factors here is the serotonin-melatonin balance; in general your brain favors production of serotonin and various catecholamines in the waking state and daylight hours, at nighttime and when relaxing/meditating/drifting off to sleep the brain favors production of melatonin and beta-carbolines such as pinoline, harman, and the tryptolines, which themselves have MAOI properties.
What I'm getting at here is a set and setting kind of thing based on biochemical composition. If you inhibit the activity of MAO when you are running the waking consciousness operating system you are going to facilitate a buildup of things like histamine, serotonin, glutamate, orexin, acetylcholine, and various catecholemines which all work to promote alertness and waking states. It's pretty simple to understand why one would then encounter sleep disturbances. This also kind of ties into the studies correlating low levels of MAO with agression/irritability/etc... That's a pretty natural response to abnormally high levels of stress hormones.
Alternately, if one is to take harmalas when the brain is running the relaxation consciousness operating system, generally one should expect them to synergize with the effects of the endogenous beta-carbolines and result in increased relaxation, well-being, and the facilitation of access to hypnogogic/dreaming/meditative states. When people take ayahuasca (or any harmala + dmt combination) they typically end up laying down, closing their eyes, and entering a resting/dreaming/meditative state. Which again promotes this natural synergy with the endogenous bedtime neurococktail and would explain why people usually report sleeping well and waking up well rested rested after a ceremony.
So the hypothesis I'm effectively pitching here is that better experiences (and better sleep) can be obtained by taking harmalas at night time, taking them while in a relaxed state of mind, taking them in conjunction with melatonin or other tryptamines, and/or taking them while engaging in practices like meditation or yoga.
There are a lot of things that can effect our natural baseline hormonal/neurotransmitter balance. As an example, people that meditate or practice yoga consistently have naturally higher plasma levels of melatonin (and likely beta-carbolines) and lower levels of MAO and stress hormones than control subjects. So engaging in these kinds of practices consistently can make a difference. Likewise, diet makes a big impact, eating foods high in neurotransmitters, amino acids, and flavonoids and avoiding refined sugars, steroidal hormones, and stimulants can make a huge difference as well.
As a side note, I doubt benzos would be very effective with harmalas because the harmala alkaloids themselves function as inverse agonists at the GABA-A receptor making them effectively anti-benzos.
