I'm buying the 55" Samsung KS9000 4K tv and I'm not willing at this time to give up on my beloved 2 channel 2150. Unfortunately, RCA connections are a thing of the past on these new TV's. What is the best why to connect this tv to my 2150. Do I need a digital signal converter? Please explain in detail my option, how to do it and any recommendations on hardware needed.

Buy a new receiver and move the 2150 to a room that just needs music. There is a limit on what the 2150 can do and assuming you want the best experience with your new TV you will want something that can handle the new codecs that HDMI uses. If you connect your cable tv/satellite box via HDMI you will get all the video advantages but the audio will be limited to stereo+sub. Since the 2150 has limited digital inputs (USB) RCA is what you got. A new receiver will provide all the new codecs and connections you need and can be had for around $500. If you have to use the 2150 because you just can't get it out of your system then connect the cable box to the TV with HDMI and then to the 2150 with either RCA or digitally with the USB input. I don't know if USB output is available on your source to use as an input to the 2150. Your TV has the Audio Return Channel (ARC) feature so if you get a new receiver make sure it can use ARC.

Well it looks like the Samsung supports Bluetooth headsets so maybe you could get the BTR-100 receiver which has the 3.5mm to RCA adapter and put that into the 2150. I have no idea what bandwidth the Samsung outputs over Bluetooth or if the to units are compatible. Anyone ever try this approach before?