In my opinion Martin guitars are the ultimate - I've had a few over the years and they just sound incredible. They can get a bit pricey, but it's simply a case of 'you get what you pay for' and they're certainly good value for money. The best site in the UK for vintage guitars is justgreatguitars.com - they don't have any Martins on there at the moment, but they're constantly adding new stock.
I have a dear Yamaha and an average Ashton and an old Eko range that has been passed down my family. Personally I think the Yamaha has better sound quality but my Ashton is an electro-acoustic. If I had more money I would probably buy myself a Fender or Gibson because they are the makes of my electric guitars which are awesome =D
