For mellow, warm, mid-bright folk-ish kinda tone, I'd recommend the Yamaha FG and F series. I have an old, beat-up Yamaha F310. Damn cheap, the lowest end of the range (costs between $250-300 brand new), but it really gives tremendous tone and a joy to play. Recommended!
Another thing about the Yamaha F and FG series guitars is that they have big soundholes, so you can easily fit quite a wide range of soundhole pickups if you get one without built-in pickup. Regarding soloing, I like these guitars because of the V-profile neck. Not sure about the other FG and F series guitars, but my F310 has a nice, slightly rounded V-profile that I find great for soloing and arpeggios.