Save yourself some headache ... and in the long run, money. Been there, done that myself.
This is a pet peeve of mine,:cussing: so forgive my longish post. :lecture:
Why get a $20,000. camera + len$e$, and then go cheap on the lighting? :wtf: Better to use a cheaper camera and better lighting. Trust me on this.:angel:
The marketing for speed-lights, and the "strobist" movement has misled many people into thinking wimpy speed-lights are a substitute for real lighting.
This is especially NOT true with MFD. It's most likely the charm of using cordless lighting, and the misplaced reliance on TTL (IMO, useless automation in real world lighting applications), that has led to the popularity of off-camera speed-lights. However, IMO, this cordless TTL desire is over-riding the logic of lighting.
If you are looking for a higher sync speed to shoot up to 1/800th, and maximum image quality of ISO 100 or 200, then you are going to run out of speed-light abilities in many ambient shooting conditions ... especially when stopping down to f/5.6 or more ... which considering the depth-of-field of MFD is a reality more often than not.
All those Nikon speed-lights you mentioned will add up to maybe 200w/s,
if even that. In reality, probably less. Use bounce techniques, or add a light modifier, like an umbrella or diffuser, and it gets weaker fast. Plus, you'd have to team them up to get enough power for a key-light in many cases.
So for example: when shooting outdoors it will be difficult to impossible to overcome the sun and balance out background and foreground when desired. If you shoot any macro, one usually has to stop down to the de-fraction limit of the lens to reasonably get anything in focus with the H4D/40. If shooting indoors ... (like a group of people), you need DOF for front-to-back focus, and some lighting spill onto the background for fill (or a background light), or you end up with ambient contamination of the subject, (which I see all the time), or an amateurish wall of black for a background. Etc., etc., etc.
I also use a Elinchrom Quadra kit for weddings and location portraits,
which I'm not recommending one way or the other. It fits my need for one man portability, consistent lighting quality shot-to-shot, and just makes it under the wire for level of power. I often augment the 400w/s Quadra by also using a Metz 54 TTL flash in the H4D's hot shoe, and mount the Elinchrom Skyport on a Kirk grip ... with a sync cord from the Skyport to the sync port on the H4D/40's body. The H4 assumes control of the Metz flash so you can compensate the level you want as supplemental fill, and the Skyport allows control of the key lighting ... all from the camera.
As a note: this Quadra is my weakest professional lighting kit. For commercial location work I have at least 1200w/s of portable lighting (Hensel Porty) + the 400w/s Quadra for supplemental light if needed ... and in studio, or large locations with a power source (like industrial shoots) I usually have at least 4800w/s with me ... along with assistants to lug it all.
When shooting studio table-top close-ups with the HC120/4 Macro stopped down for DOF, I've often run out of lighting even using a 2400w/s Profoto D4 Box!
End of rant ... apologies where due.
-Marc