Audio question

[umterps98]

I am new to the forum. I am looking at blu ray players and have a question regarding audio. I have an older Sony STR-DE545 receiver with no HDMI inputs/outputs. It has optical digital audio and 5.1 analog multi-channel. I have a Sony 46 inch LCD that obviously has the HDMI inputs/outputs. What is my best option for getting the best sound? I am looking at 2 Samsungs (1600 and 3600), a couple of Panasonics (60 and 80), and an LG. From what I understand, if I want to be able to take full advantage of HD sound, such as TrueHD, I would either need to get a receiver with HDMI inputs/outputs, or get one of the blu ray players with multi-channel 5.1 decoding. What happens if I just get one of the blu ray players without the built-in decoders and chose to use digital optical? Would I still get stereo surround sound, or only 2- channel audio? Is the difference in sound worth getting the player that costs $150 more? ANY help would be greatly appreciated.