Which Groupset?

Anyone have any experience with putting modern 10/11 speed gruppos on older steel frames with 126 rear spacing? I want to keep the frame if possible but then kit it out and money is not so much an issue as I get a very good discount. I'm open to suggestions. Is this a complete waste of time as I should just get a new bike?
I've got an 80s Moser running 2011 Chorus. Works like a charm and is the bike I'll be riding the Roubaix on in a couple of months.