Yup, Bumblebee said it to the point.
Let me just add that HT is part visuals and part audio. It's the audio part we're concerned mostly when talking about receivers and speakers. So regardless of whether it's 5.1 or stereo, your receiver and speaker combo must be excellent as an audio playback system. Audio in HT for the most part, except with explosions and opening/closing music, is slightly less demanding than full music playback over a longer period of time. HT mostly has vocals and we know the limited spectral range of vocals compared with the full range of a musical piece in whatever genre. The only thing demanding in HT are the low frequencies in explosions and other special effects which are rightly taken cared of by subwoofers, not so much by the receivers and speakers. Still, even if you don't have a sub, a great receiver and speaker tandem that is good in music can do the job for HT's LFE though on a weaker scale.
So apart form the fact that your aural faculties are less keen with HT due to the fact your eyes get more stimulus and competes with your ear's attention, a receiver+speaker tandem that does a great job reproducing the entire 20hz-20khz spectral energies of a musical piece over extended periods of time, there is no reason to doubt it can do a great job for HT.
But not the reverse. Expereince with those frequency-challenged BOSE cubes and subs show that they can be impressive with almost any HT material. But once they go plain stereo music, they start to sound pathetic.