@OP: If I understand you correctly, you want to have casual movies/music experience at home, without doing much modification in your room. Well for that, I would suggest you go with a Marantz 5013 Avr + jamo s35 hcs 5.0 speaker + 10/12" sub. Reason for these items:
1. Marantz 5013 Avr : It have pre-outs for all 7 channels, so, you can add external amplification in the future if required.
2. Jamo S35 5.0: They are a pretty small, still powerful speaker and they can easily mount on walls or placed on desks. I am using them and found that they will be pretty suitable for your scenarios. Keep in mind, they are not the best sounding speaker for their cost, and compromises are made to get them that small design.
3. Sub: Those Jamo speakers lack base, so, a sub is a must with them.
1. Marantz 5013 Avr : It have pre-outs for all 7 channels, so, you can add external amplification in the future if required.
2. Jamo S35 5.0: They are a pretty small, still powerful speaker and they can easily mount on walls or placed on desks. I am using them and found that they will be pretty suitable for your scenarios. Keep in mind, they are not the best sounding speaker for their cost, and compromises are made to get them that small design.
3. Sub: Those Jamo speakers lack base, so, a sub is a must with them.