Yes I have the 550W as a potential replacement to the 600HPS. I am currently using it to veg the moms but can honestly say I think it will rock the space, just the veg spectrum with the UV's seem to give me a headache just hanging around the moms, and when the flower spectrum is on by itself it is as red as fuck!!! The growth under the veg has been much quicker than under my flouros and the leaf development has been much bigger.
The 260W I linked I think run 160W with both spectrums on and has a core coverage of 3x3 which I think beats the blackstar at 2x2.
Either way I like mine, it is well made and Benjamin the guy who owns the joint is a decent guy, he will probably give you a discount, he gave me one.