I don't know very much about the specifics of Muslim polygamous marriages, but my first reaction to your question is that marriages for aristocrats were by and large pragmatic (Muslim or Christian / polygamous or not). For alliances between families or economic benefits or for a number of other reasons. On the off chance (because I would imagine it was relatively rare) that an aristocrat would fall in love with a peasant, there would be little incentive for that aristocrat to marry the peasant. I think it would actually be quite scandalous for the aristocrat to do so, and that individual might be ostracized by his/her family and socio-economic community. Instead, it would make much more sense for someone of aristocratic status to marry pragmatically, keep their economic and social status intact, and to perhaps continue a romantic relationship with the peasant as an affair (whether as an official concubine, if applicable, or just a lover).

This isn't, perhaps, the most romantic notion, but I think the idea that marriage is the ultimate confirmation of romantic love is a relatively modern concept. Marriage, up until relatively recently in social human history, has been largely a practical arrangement, though it is certainly possible that married couples throughout history have been in love.