I downloaded my Kurosagi from d-addicts, subbed by Kioku, the quality was pretty decent. I downloaded the raw version of the first episode, the quality was awesome since there were no compression done. Kurosagi was filmed in darker tones, I think the producers were trying to tell the story with a
film noir feel to it. I do feel the show was pretty predictable in many episodes, and I seriously do not understand some of the tactics Kurosaki used to swindled his opponents. Some of them were just too far fetched while some were just 'huh?' to me.
The female lead is Horikita Maki, the love story wasn't really a love story, it was all along one sided, Kurosaki never expressed how he felt about her. I suppose it leaves the possibility of a sequel?
The PV of both Seishun Amigo and Signal can be found in youtube. If you want high quality versions, then you probably have to download them.