Since you mentioned the Samsung 840 Pro so I am assuming you are looking for a standard 2.5 inch SATA 3 6Gb/s ssd and not one of the other 3 types.
I normally recommend Samsung. Their ssd's perform exceptionally well and have a proven track record. The 840 Pro was Samsung's flagship model. Recently it was replaced by the new 850 Pro. However, the better "value" is the Samsung 840 EVO. It is the number one best selling ssd in the world. At the beginning of this month Samsung announced they would be releasing the 850 EVO model in the very near future. Crucial, SanDisk, and Intel are also worth considering.
I maintain the ssd database listed in a sticky at the very top of this forum section. Here is the link...