I can recommend you LENOVO G580, 120 GB SAMSUNG SSD, 8 GB 1600 MHz of RAM and i5-3230M CPU @ 2.60GHz. Bought it 3 months ago for 2000 PLN.
1 PLN = 0.330863 USD, so it was 660 USD.
Works very well, the only thing which might be not so good for Tibia is resolution, 1366x768.
Good thing is it can work 4-5 hours on battery.