don't most of the later cdi players support power input 100-240 volt at 50-60Hz ?
If that is the case, you would not need a step down converter, just a different power cable (or an adapter).
The CDI-740 player is last model Philips released, it is a beautiful player and very rare, and has the most options of any consumer cdi player (I'm selling one on ebay right now, ending tomorrow).
The Kyocera and Digital Video Systems players are also hard to get. I don't have them, but they seem very nice on the pictures.
For a full comparison between players visit the international cdi association website:
http://www.icdia.co.uk/players/index.html
I think the Philips CDI-370 (or goldstar equivalent) is probably the most useful player. It is small and portable, has it's own LCD screen, a replaceable memory battery, outputs NTSC or PAL and has all the options of the bigger players. (BTW, I'm also selling a Philips cdi-370 on ebay, ending in a week).
The cdi-470 (with Digital video cartridge) and the CDI-490 are good budget solutions (especially the 470 can be bought cheaply).
The cdi-450 is also cheap, and is imho much nicer looking, but doesn't come with a infrared remote by default, and has more limited connection options.
A lot of the older CDI-210 and CDI220 players have problems with the memory battery, so you can't save your games.
A lot of the newer revision cdi-220/60 and cdi210/40 players have reading problems (the cdm 12.4 laser unit, that was used in these revisions of the models was known to have a high failure rate, the older CDM9 and the later cdm 12.1 laser units are better).
You should try to get the last revision of the CDI220 and CDI-210 if you want those models (the cdi220/80 or cdi210/60). But these are somewhat rare.
The revision numbers I mention here are for the European (mainland) players. In the UK and the US there are slightly different, but you should ask an (ex)philips employee how the system works. I believe all US revisions add 17 to the revision number. So the European CDI-220/20 would be equivalent to the CDI-220/37 US model.