Furutech FI-48 NCF (R) vs. FI-50 NCF (R)

This is exactly what I used for the cable for my streamer/CD Player (modified Oppo 105). The sound is a tremendous improvement against a ~200 EUR commercial cable. I used the Furutech Rhodium spades (FP-209-10 (R)) to terminate the cable ends, they fit nicely with the cable clamps in the higher end Furu connectors (starting with the FI-28). You need a decent crimp tool though.

Can't comment on the FI-48(R), but the FI-48(Ag) is great in my system. 

Without doubt the best silver-plated connector I've ever auditioned!

I have only used DPS-4.1 with the FI-50 plugs, so I can't say how they would compare to the other Furutech plugs but I can certainly recommend the 50s. The sound is beautiful, super detail in the midrange, bur zero harshness, and excellent soundstage (depth). Bass is good too, but probably you could find something better at this price point (for me it's good enough). The Polish Furutech dealer terminates the DPS-4.1 with FI-50 only, saying it's the only combination to go (in fact this is the only termination he agrees to install...).  A word of caution though: the DPS-4.1 with FI-50 takes endless hours to break in, so you will really have to patient before the magic hits you one day :) The changes during the breakin are evident in a high-resolution system, they may not be so dramatic in other systems.