Dan will make his own reply.
I own both the original, first series BUMM IQ Cyo lamps, the 60 lux "racer" version without a reflector, and the 40 lux version with the reflector, and of the two I much prefer the reflector version. For practical purposes, both have tremendous reach and are suitable for fast riding on pitch-black roads but the 40 lux version has more sidespill close to the bike than the 60 lux version, which is extremely useful for positioning the bike on unlit roads and lanes where you want to see the ditch, and even on the darker streets where you need to see the pavement edge, and the car door opening into your path before you hit it.
The BUMM IQ Fly has the same optics as the Cyo and is a spot less expensive. All models Fly have a reflector, and the standoff mount is built in.
Now it gets complicated. There is a second series of BUMM IQ lamps, in which BUMM buggered around with the optics, and buggered them up. I have the IQ Fly from the second series, again the same optics as the second series Cyo. It has a distinct and seriously disturbing hotspot and BUMM has given you nothing in return, certainly not a wider throw of light.
I would therefore advise you to see if you can get a new old stock (NOS) first series Cyo R (the official name of the 40 lux reflector model). It is useful to have the Plus, which has a built-in capacitor for a very reassuring standlight. Or, less expensive, a first series Fly. In each lamp there's a special, switchless version for sidewall dynamos, in theory cheaper but probably not discounted as it is rarer, so you may as well buy whatever is cheapest, including the nominally most expensive model, the Senso Plus, and just switch out the facilities you don't use until you get a dynamo wheel.
You can see the Cyo/Fly 40 lux light pattern at http://coolmainpress.com/BICYCLINGbuildingpedelec6.html
You will see the hotspot in the photographs and how narrow the throw is in the lanes. Also how little sidespill there is from the lamp with the MOST sidespill... Notice how in the photograph with striped speed bump the fence the road worker put up, literally inches from the edge of the light, is not lit.
The Cyo in its day, despite these shortcoming, was the best lamp you could buy. That is not necessarily true after they bolloxed the optics. If you can't find an NOS first series Cyo, I would advise you to pay serious attention to the Philips SafeRide, which is commonly considered a better lamp than the current series IQ Fly/Cyo. The problem with the Philips is that it is outrageously expensive. But perhaps you can find one discounted on the net.
Some beamshots here but be sure you're looking at the lamp you're buying, not a different lamp of the same name... http://www.fietsersbond.nl/de-fiets/onderdelen/verlichting/krachtige-koplampen-test-2011/philips-saferide-led-dynamoversie
Of the SafeRide the tester concludes "Verreweg de beste lamp om onder alle omstandigheden mee the fietsen." -- "By far the best lamp to cycle with under all circumstances." From the beamshots, i particularly like the amount of sidespill -- you could ride offroad on a single goat track with this lamp, and not come a cropper, as you're sure to with the Cyo/Fly narrow/far paradigm. Also beamshots of the Axa Nano, recommended further up this thread for its USB port; I don't find its beam all that impressive in this company.
PS If you're buying a Cyo, order the best light bracket in the business, B&M's 471LH, at the same time to save carriage. This is an unbreakable nylon bracket (not "plastic" as SJS has it!), taller than normal so the light shines even over fat tyres from 47mm up without any dead spots. http://www.sjscycles.co.uk/b-and-m-light-bracket-in-plastic-long-471lh-prod22450/
Standard equipment on Utopia, to whose specification it was designed. This bracket damps vibration most effectively and has channeled wire routing.