Apart from my seedbox, I own a small NAS, 600 MHz ARM CPU and I can tell you that transmission-daemon sometimes hog 100% the CPU with about 400 torrents active. Of course it's not comparable with your masterpiece project, but just to give you a figure.u should definitly go with a rtorrent/rutorrent solution instead of transmission then, cause the performance with that many torrents will be much better.
Figyelem! Szexuális ragadozók az nCore-on! Kattints a képre!