a bit of friendly advice:
whatever you do, don't buy HID units - these are rapidly becoming obsolete. I bought a Lupine Edison 5 which was hilariously bright (900 lumens) and as well made as anything I've ever seen in my life. Just after spending a smidgen shy of Â£400 i learned that Lupine had just released their improved Wilma 8 which is an LED system, almost as bright at 830 lumens, has better features (ie SOS flash, infinitely variable dimming, instant switch-on, long battery life and flash mode, also Wilmas are upgradeable as LED technology moves on) and is about the same price as what I paid for mine at Â£400 (rrp for a Edison 5 system is Â£550-570). Plus when the lamp goes on your Edison you're looking at Â£100 and maybe a month out of action as you send it back for a new welch-allyn bulb.
I should add that I sold my edison on ebay straight away without really using it and managed to get 99% of my money back on it.
This also means that bargains are available, there's an Edison 5 on th'ebay at the moment http://cgi.ebay.co.uk/Lupine-Edison-5_W0QQitemZ260157801002QQihZ016QQcategoryZ22689QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Ala Carte Ti, Mantra, Attitude, ancient steel Trek