System Placement Question

Well you could turn the radiator off and go to HD to buy an attractive radiator cover made of wood.And if it gets to cold then buy a class A amp. That should keep the place warm enough or get a space heater just for those cold months.Studio apts are a challenge but can be workable.

How about switching to a big pair of Class-A monoblock amplifiers -- Krells come to mind -- and then turning off the radiator, leaving the amps to heat your place?
Just a thought.

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.

How wide is the room and how long is the radiator? Would you be willing to purchase longer speaker cables to put the rack and TT on the side wall?

IF you live in a cold climate, (where the radiator is going to be ON, full force for months..) then do not place your stuff anywhere near it, unprotected. If you live in a tepid climate, where the radiator will be on only sporadically, then it would not be so bad.
Then is the radiator using steam? or hot water. BIG difference. Steam is way hotter.
The heat from a running for months radiator will dry out your cabinets and damage them. If it is on only occasionally, not as likely (but still could happen if too close.
The electronics will have a shorter lifespan if heated by the radiator, but if you place an insulated board between the back of the rack, and the radiator, I think it would be just fine. (Better to have the board very close to the rack, and leave at least 6 " clear between the board and radiator. better if 8") thus the natural convection of the rising radiator heat will be unaffected.
(And depending on your building and the outside temps, you may really WANT all the heat you can get.)
I live in a cold climate. My Bryston 4B-SST2 is a foot away from the baseboard hot water heat. Not worried as that is an outside wall, and the big window above always has a cold draft off the glass..