What to upgrade next.


This is my first foray into the forum other than reading other's post. I hope respondents will be kind! I am at the very low end of audiophile equipment and many of you may not think I am there yet when I list my equipment. The economy has become better for myself and I am looking to upgrade but not exactly sure where to go from here. I am sure I will receive many different suggestions so I plan on taking the one suggestion that I receive the most and employing it. My equipment is as follows: Denon AVRx 3500H as my integrated amp which is boosted by a Bob Carver Cinema Grand 5 which pushes 200wpc. This powers my Polk Audio RTiA7's which are my music floorstanders. When I started upgrading I chose the Polk's as they seem to punch above their weight. After months on this site I am unaware of many people who extol the virtues of the Polks so I am thinking this may receive the most as far as recommendations. I stream most of my music from my desktop and laptop. The desktop sounds like an airplane waiting to take off. I am not independently wealthy but am looking to spend between 2-3 thousand if necessary. The one thing that gives me the biggest headache at this point is music delivery as computers have glitches and my angina acts up when the music cuts out in the middle of Alex Lifeson shredding his axe. My music files range from bad copies of MP3s which are slowly being replaced to HD Audio files. Thank you for any suggestions.
dadork
 Tom @tom8999 I am sure now because of all of the comments that Source as you said is the biggest issue. I have committed to buying the Bluesound Node2i as my first priority. I have just enrolled in Tidal HiFi. For the time being I will stick to my Carver Sunfire Cinema for amp so I guess that leaves pre-amp integrated amp and speakers to upgrade. Thanks!
@mesch I am committed to buying the Bluesound Node2i and getting the Tidal subscription. I think Tidal will relieve a lot of my headaches I have with my music files and give me a much better file to boot as far as Hi Fi or Hi Res. I think now I am getting a clearer picture too as why I need a pre amp as opposed to an integrated. Tell me if I'm on the right track. Seeing I have a power source for all 5 channels when in HT and of course in 2 channel for music I don't need the integrated because I am bypassing the amplification provided by the Denon integrated. If I understand the theory right I am running my music through something that muddies it up. If I just get a good pre amp that doesn't add the amplification it keeps my music files cleaner.Will it still have thew video processing or passthrough and all of the HT features that I currently enjoy?
@spenav Thanks! I know already that this pool might be a little deeper than I thought. I do however have to set my limits and I think landing around the $10K range is a system I can be happy with and know that I am hearing everything to be heard. I do plan on buying used equipment , especially on AG. Thanks for the advice.
@mesch  You brought up room size and configuration. My living- listening room is 11'5" x 25'. It is an odd config as the only place to put the speakers ( On short wall)leaves my right channel open to the right into the dining room. The left channel is set next to the long wall which has an 8' long window. I have heavy drapes which I can close to block reflection but not sure what's best. I have run it through the Audyssey and I leave the Dynamic EQ off as well as the Dynamic Volume Control. I listen in 2.1, as I mentioned my sub is sub par. Listening now through the Tidal certainly improves things quite a bit. My wife thinks I'm obsessed, which I guess is true. I'm constantly moving by speakers by inches always keeping with the directives of similar placement ie. distance from back wall, side wall and toe in. My listening perch is a sound sucking, sound blocking overstuffed recliner placed 14 feet from front of speakers with the speakers having 10' between them. I have done the sub crawl and somebody might be laughing another sucker fell for it but so what. Right! I live in the far north boonies of Michigan before you cross into the wilderness of Da U P. This means places to audition higher end equipment is more than sparse. Reviews and advice are my best tools at present so I am more than willing to talk and learn. I don't know a lot about treatments but I do know of them. Not sure on specifics as far as placement.
Good move on Tidal subscription. I would get it as well if I had better internet connection. I think the Node will serve you well. May want to get a external DAC as an upgrade down the road. 

Given your system is for audio and video, I think your next move might be to purchase a preamp with HT passthrough. You can use the pre into 2 channels of your amp for  R and L and pass signal to the Denon for the center and rear channels when watching movies. Provided the right connection are provided on the Denon. I once owned a Jolida Fusion tube preamp that had this function. Did not use the HT feature but it was a nice unit which sold retail at $1350. Sold it here on AG recently for $750. Ran it with a SS amplifier.  You are wise to take advantage of the AG marketplace. I have used it extensively over the past 9 years. Made some friends along the way.

One thing I should have suggested from the start is to recommend the book "The Complete Guide to High End Audio' by Robert Harley. Great reference book. Runs about $50.

Stay safe, continue your homework, and enjoy the ride.