If you're a 'collector' and this is a real PAL Turbo, then YES, it is definitely worth it.. the 'official' PAL Turbo Grafx 16 was very rare and got almost no support from NEC or Hudson and hence doesn't appear very much.
If you just want to play the hundreds of PCE/TG16 games, then a US Turbo Duo is the way to go - plays all US/Jap CD games, native US hucard games, and with the aid of a convertor (http://www.tzd.com) will play all Jap hucard games.
Once you've got one, then get a white or grey PC-Engine (Core Grafx / Grafx II), to play the few final Jap games which won't run on the US system, or only with Jap bios cards. Plus, they're dinky and look so cool!
PS. I've got the 'cheap' green diving board convertor, and it plays all my Jap games fine (including SF2 CE), on both my Turbo Duo, and my Turbo Express.