Denon 1312 is a good entry level receiver, go for it. It is unfair to compare such reputed brilliant speakers to entry level satellite systems. You can't compare Mission 34i/34i to JBL Cinema 300............no comparison!!!
You have to make a choice........fantastic tower speakers vs entry level 5.1 speakers. choice is yours. For music a 2 speaker pair is the best way to do it. The sound you hear will be more superior and complete compared to any entry level 5.1 system. A 5.1 system is more suitable for movies, so all depends on what your requirement is. Any good stereo speakers can also play movies effortlessly.
I would definitely go for Mission and then down the way add more speakers eventually making a complete 5.1 system.