This mix talk makes me realize that I've never watched Evangelion with the 5.1 mix because I've never had a proper surround system. I'll have the watch the series with the 5.1 mix if I can get my hands on the bluray.
This doesn't make sense. Are you trying to say "I never experienced the full sonic fidelity that is a discreet 5.1 audio mix on a killer hi-fi surround sound system" or are you literally saying "I've never listened to the 5.1 mix because I switch the audio track to the stereo mix because, you know, I only got two speakers; where are the other 3.1 channels gonna go?"?
Platinum only has 5.1 mixes. Renewal defaults to 5.1 (as I found out, you have to switch it to stereo and then you hear the broadcast mix). Original US and Japanese DVDs only have the stereo broadcast mix.
Even if you have 2 speakers, DVDs and Blu-ray Disc players (as well as TVs and audio receivers) are designed to downmix multichannel audio to stereo, unless bit streaming is set (there's a bit more that goes into this, but for reasons, let's just say this is normal). So even if you have only two speakers, a 5.1 mix will still play in stereo. L and R obviously go to L and R, C is lowered (?) by 25%(?) and sent to both L and R, and SL and SR are lowered by 50%(?) and sent to L and R respectively (my levels adjustments may be off, but that is essentially how downmixing works). LFE is usually nixed unless you have full range speakers or a separate subwoofer. So you still hear everything even if you just have two speakers.
But yeah, you should experience this on a 5.1 surround sound system. Even scenes as simple as the Command Center are given so much space. There are techs on the rear channels talking up a storm and just lends to its environment.