As far as standard CD versus 2-channel SACD, if you're happy with the sound you're getting, then "don't fix what ain't broken". You would, however, notice a BIG difference with Surround Sound - but to use it, you would need a Surround Sound system, be it a home-theater sound system that you could buy for quite a bit of money, or a Surround Sound card (I use Creative SoundBlaster) on your PC and some fairly inexpensive Surround Sound speakers (maybe Logitech) to go with the Surround Sound card. (Or you can also get quite a bit fancier & more expensive if you like.) You should be able to get some very good speakers and a good surround sound card for no more than $300, but it just depends on how picky each individual is.
I use a Creative Soundblaster Zx Sound Card (
https://www.amazon.com/Creative-Blaster-Performance-Headphone-Desktop/dp/B009XDWUCQ) and Logitech Surround Sound speakers (
https://www.amazon.com/Logitech-Surround-Theater-Speaker-System/dp/B003VAK1FA). I live in a fairly soundproof apartment, so this setup works really great for me, but I can't "blow the walls down" too much either, so tower speakers with 12-inch cones and a theater system that includes its own electric power grid separate from the local utility company would probably be somewhat annoying to the neighbors.
Of course, if you live out in the country and money is no object, then you might consider a setup like this.....
https://drive.google.com/uc?export=download&id=0B6U4A_vYuii5Zl9SMXk5MWFNUmM
https://drive.google.com/uc?export=download&id=1RxmqaAVVAtwqiVOiIeW3ppFK9uB6cmLx
https://drive.google.com/uc?export=download&id=1hcNDRLWVkl8uEwyNAzSkv_aDEiFGjhnk