It depends - what motherboard do you have? Can it support SATA III? If not, a SATA II drive is cheaper.
Get just the one - the larger an ssd is, up to about half a terabyte, the faster it'll be.
That is a good price, yes, and a decent drive. The order of preference based on reliability and speed:
Samsung 840 pro
OCZ Vertex 4
Samsung 840 non-pro
Intel 300 series
OCZ Agility 4
Mushkin Advanced Chronos
Generally you want to stay away from other drives, due to reliability problems.