Which are the most versatile high end speakers

I am putting together a Naim system with cd5/112 preamp/150 amp (50 wpc) and would also like to upgrade my speakers.
I currently have some KEF's with Uni-Q drivers which I like ok but my taste in music is pretty diverse. I like rock/metal as well as classical. What would be a good starting point into the higher end speakers. So far I have had the ProAc tablette 2000 and jm labs speakers recommended, I have also considered auditioning the Shahinians but have no dealer in my area. I like a speaker which can deliver bass when called for.
Of the ones I've heard, Dunlavy SC-IVAs and Alon II and V speakers seem to meet your criteria. Both can deliver the goods on rock and classical. Sure there are plenty of others out there as well, these are my favorites.
Dallas- Speakers seem to be the most "personal" component in any system. You'll probably not know if a speaker is right for you, until you've lived with them for a while in your system. With that caveat, I'd suggest that you consider the Coincident Speaker line. Also, since you obviously enjoy the NAIM line, checkout their speakers. Both offer models that can work well with your electronics. Good luck in your search.
If versatility to you means a speaker that will handle virtually all types of music, you have essentially defined a good, full-range speaker. One of the best, reasonably priced, full-range speakers on the market is the Vandersteen 3A or 3A Signature. They handle virtually all types of music well -- I have a pair of 3A Signatures and they do a fine job playing everything from small chamber music and jazz quartets/quintets to full scale orchestral music and rock.
I agree with Sdcampbell, in any respective price range, look no further than Vandersteen Audio. No hype, just pure music. I also have the 3A Signatures.
If you're into rock / metal then a sub might help your setup (subs also add a lot to full orchestral classical pieces ... more than you might expect). Try either REL, or perhaps home demo an ACI titan (which many seem to like, and works in a pre-power amp setup). I have a REL strata 3 ... it has transformed my system, and now I can listen to choral music, chamber music and rock and it all sounds great.

A sub frees you up from having to purchase true full-range main speakers, and it also allows you to place the mains optimally for soundstaging without having to worry about bass reinforcement. (Of course I'm not considering the WAF in the speaker placement). Also you can choose mains for their soundstaging and tonal characteristics, rather than having to settle for something with the last octave in bass.

However I wouldn't add a sub if the mains are already a bit bass heavy.