I would buy the Ruby Comp Disc that is $400 more than you planned to spend. Comparing the bike Muirenn linked to and a Ruby Comp Disc that is $1950, the components on the more expensive bike are two levels better and in my opinion are worth the investment. And it's comfortable for you, which is very important.
I can't speak to disc brakes vs rim brakes, since I've only used the latter. There is a thread or two discussing the advantages of disc brakes somewhere on this forum, should be something you can find by searching.
- Gray Trek Madone 4.7 road bike, mystery crack in top tube repaired by Calfee, Bontrager Affinity RXL saddle
- Red Trek 6000 mountain bike, Bontrager Evoke WSD saddle
Gone but not forgotten:
- Silver Trek 2000 road bike
- Two awesome and worn out Juliana saddles