I'll add my 2 cents to what Seandtaylor99 said about the Rel integration. I also can't address the Spica TC=50's, but I have a Rel Storm I, and a Storm III. I've run the III with Totem Sttafs, and now it's set up with Mani-2's. I ran the Storm I and III with GMA Europas (at different times, of course). I found it easiest to integrate the sub with the Sttafs by far, and hardest with the Mani-2s. The crossovers were set at 35 Hz for the Sttaf, 48hz for Europa, and 29Hz for Mani-2. My hypothesis is that in general, the higher the crossover is the easier it will be (although I expect there's a knee in the curve if you go too high). I think the sweet-spot is in the 40-60Hz range. With the Mani's, the sub isn't even in play for most music, and it almost doesn't make sense to have it. Further, I think (conjecture on my part) the only reason Europas were more dificult to integrate is because they're phase coherent/time aligned and I had to fiddle with the positioning of the sub a lttle more than for the Sttaf.
The Rel/Sttaf, and Rel/Europa combination is really satisfying, and even though for the money you can get a full range, It may not have the quality of deep bass, and perhaps not the quality of the upper bandwidth either.
The Rel/Sttaf, and Rel/Europa combination is really satisfying, and even though for the money you can get a full range, It may not have the quality of deep bass, and perhaps not the quality of the upper bandwidth either.