With Sora , you get only 8 speeds on the rear. Sora also has different shifters , with the "downshift" levers on the inside(you use your thumbs) instead of behind the brake levers.
My main bike has a mix of 105(shifters, Brakes, and Front Derailleur) and Ultegra, but it's older 9speed stuff, I've got about 12,000 on her and she still shifts fine. I did replace the cables, though.
You may also want to look at Tiagra if you're on a budget. It's Shimano's group between Sora and 105. It's 9 speed.