My first Yamaha was an FG580 - 6 string, Brazilian Rosewood Nippon Gakki model. According to the brochure (mid 1970s) it was top of their range of hand-crafted FGs. I was really looking for a 2nd hand Martin and found the FG580 advertised in the New Musical Express. This guitar was my all time favourite for 25 years.
After years of searching and trying many 12 strings I eventually tracked down an FG630. According to that same brochure this was the top notch stablemate for the FG580 - same woods but with a slotted headstock.
My favoured strings were D'Arco New Yorkers, but when they became unavailable I moved to D'Addarios. Later moved to Elixir Nanowebs and never regretted it.
Both guitars have a big big sound, maybe the bass end a little too much. Recently they started to sound a little 'tired' - replacing the bridge pins with brass ones revitalised the sound somewhat; brighter, with a better string separation kinda feel.
In 2005 we bought a CPX15A 6 string and CPX8-12 12 string which both sounded great in the shop and at home and through a PA, but didn't cut it in an acoustic folk club environment.
4 months later the CPXs were sold and part-ex'd - our performance guitars are now Taylor 810-LTD, Taylor 810CE 6 strings and Taylor 855 12 strings.
Couldn't bear to part with the Yamaha FG580 and FG630. I occasionally play them at home (they're old friends) but, now being accustomed to the Taylors, find the neck difficult by comparison. They still sound good, but to our ears not 'as good'.
Jimmy & Val