A good review:http://www.computerbase.de/artikel/netzteile/2013/be-quiet-system-power-7-450-watt-im-test/
You asked about fully modular PSUs, that's why I suggested Silverstone. BQ system power 7 units are not modular. Other things I don't like about this series is the dual 12v rail design and lower efficiency than ST55-G (at least on paper, linked review confirms that it meets 80+ silver).
If you can fit non-modular 140mm deep PSU and can balance the load between two rails, then System Power 7 series is worth considering. In this case, also have a look at Enermax Naxn series.
Personally I don't like Be Quiet PSUs. Two of them - Straightpower and dark power pro failed on me just after their warranties. Thus, I don't recommend them to anyone.