Unless you are going to upgrade to high end SLi configuration, you will not need a 700W+ PSU... Well, unles you also want to install 8 mechanical drives and an addition raid card with 4x or more HDDs. ^_^"
A 550W supply is definitely enough for your current configuration. However, if you are planning to go for 7870 CF, GTX670 SLi or above, you might want to consider something more exotic.
If you want a cheap $50 after mail in rebate (US), reliable and non modular (with the power connectors permanently attached) PSU: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Please notice, the default configuration and intend of both of these PSU are not designed for SLi or CF config. You might be able to get away using the molex to PCI-E 6 pin connector but I still would not suggest doing so.