What can I improve in my audio system for better s


I have lossless FLAC music ripped from cd's and music I purchased from HD tracks, I am using Macintosh MX 121 processor, Krell S1500 7 channel power amp, 7.1 SYSTEM, B&W 802D speakers for front and center, Monitor Audio for side and rare channels, Crystal and Audio Quest for interconnect and Tara Lab for Speaker cables. I am using JRiver to play this music from my computer, which resides on Lenovo Q180 small foot print PC with build in HDMI which is connected to my processor via this HDMI. I don't know why but I feel that this PC is the least expensive equipment I have, and is the weakest link in my entire system. There is nothing wrong with the system. But, it always bugs me that I can improve this weak link. I like the fact that while playing music I can see the album cover and track information on the monitor. But still I am curious to know, if possible, how I can improve the sound quality. Since I have a McIntosh processor with built in DAC, I don't want to add another DAC (by the way I tried using Moon DAC, it was no-ware close to McIntosh MX121, ended up selling it on eBay). I am not even sure, while using HDMI port does better sound card matters? Or can I enhance anything in my system to improve the sound quality or am I looking for unrealistic Magic? When I purchased this system, my friends were so surprised from the money I spent, there first question to me was "Does singer comes out of these speakers to sing for you?" I guess that's what I am expecting; I believe I am missing those emotions that we get from live performance.

Need a professional advice, please help.
trcns
You have good stuff. What aspects of the sound do you think need improving? How do you know what your target sound is or equivalently where yours is deficient? Have you heard some other system for reference? IS there any noticeable noise or distortion?

There is no absolute sound. Its often highly subjective what sounds better or best.

Some more info might help others make more useful suggestions.
Also a system picture showing the physical layour would help. Often all that is needed for better sound is a better approach towards setup and dealing with room acoustics. Definitely a best practice to get that right first before changing anything.
"Or can I enhance anything in my system to improve the sound quality or am I looking for unrealistic Magic? When I purchased this system, my friends were so surprised from the money I spent, there first question to me was "Does singer comes out of these speakers to sing for you?" I guess that's what I am expecting; I believe I am missing those emotions that we get from live performance.

Need a professional advice, please help."

You're making a very common mistake. You have no way of separating reality from fantasy, with regards to what's possible. What goals have you set for what you want your system to sound like, and are they based on a system that you actually heard? If you don't have any clearly defined goals that you know can be achieved, it will be one guess after another with no end in sight. Yes, I know its harder to do it this way, and that most people will tell you to just buy this, or buy that or whatever. That approach doesn't work.