If your amp and CDP are kept to the side and your speakers can be pulled away from the wall and spread far apart from the radiator you have no problem. If OTOH the speakers still will actually get hot from the radiator then...You are stuck using the long wall. Just research the numerous threads, white papers, ratios, triangles, various ancient texts, and religious belief systems, damping materials, baffles, busters, deflectors, absorber, to get inspiration for the reiterative process of moving your speakers around until they sound best from the listening position while decorating your apt at the same time. I never did get my wife to like the hanging sheets of Dynamat, no matter what color they were.