Your single biggest problem here is that the salesman told your boyfriend that buying a home theater set (an AV receiver?) would reduce the sound quality. Frankly, nothing could be farther from the truth, but since that's what he believes now, your options get a bit limited. As others have said, several of the Denon AVR products would be fine. They can and will drive the speakers without compromise. There is no need to add a separate 2 channel power amp, other than the firmly implanted belief system the salesman installed in your boyfriends mind. Unfortunately, there's no easy way around that, but fortunately there are a few excellent and inexpensive solutions from Emotiva. If you do that, a less expensive AVR would be fine.
You have a sort of system design mess on your hands though. Ideally, all three front speakers should be identical, or at least similar in sound. Buying a radically different center channel speaker now will create a discontinuity. The center channel, in movies, carries more than 70% of the total sound in a home theater, so it's the most important speaker, but often gets treated as a second-class add-on. The surround speakers you'll want for 5.1 channels are somewhat less critical, but again, ideally should be at least similar in quality to the front 3. Subwoofers are probably the least critical of all in terms of match, and the choice relates mostly to room size, position, and available power from the sub.
So, back to step 1, pick out a good receiver, one of the Denon's or Marantz units mentioned, consider a stere power amp to make him feel good, and work on what you'll want for center, surround, and sub as you move forward. Make the AVR the center of your system.
One more thing, the idea that 2 channel stereo music is somehow "pure" is completely wrong. Stereo is a compromise. The original experiments done at Bell Labs in multi-channel sound determined that more channels is always better, the ultimate would be a grid of thousands of speakers (essentially a speaker for every possible sound position) and the minimum channel count for a reasonable sound stage was 3, left, center and right. We got stuck with 2 because of the limitations of the distribution medium of the day, vinyl records. There was no good way to get more than two channels on them, so thats what we got. Stereo only works right when the listening position is exactly on a center line between the speakers. Any other position presents significantly out of balance stereo. Three channels extends the listening window well left and right beyond the center line. Two channel stereo is hobbled by nature, but that's what we have. Many AVRs have ways of re-channeling stereo to 5.1 surround, and some of them work pretty well. Just some background info that may become useful some day.
