What to upgrade next.

Hi,
First of all, if you have an Apple computer get Channel D's Pure Music program. If you have a PC get J River's program. If you do not have one already get a good USB DAC, there are many on the market. You are already getting rid of the MP3 files. I generally use HDTracks for down loads. Next sell the Polks and get a pair of Klipsh Cornwall IV's This will make you VERY happy for a while. When more money comes in down the line get either a DEQX Premate or Anthem STR . These are digital preamplifiers with huge power. Next comes an amplifier. With the Cornwalls you only need 100 watts/ch and I would recommend a tube amp such as a Carver, Manley or Mcintosh. Finally, two subwoofers. You would already have the best crossovers in the preamps plus room control so all your need is a passive sub. If you are handy, building a sub from Parts Express would be tops and very cost effective. Now you can just collect music:)

Well given you are now considering a 10K system the 'plot thickens'. A very good system can be had at this price level.

I have a couple questions that will help in providing advise.
What is the room size where this system is to be placed?
What is the timeframe for completing this system?
What computer and file type are you using?

There are many ways one can approach this. I also started towards a 10K system, spent 8-9K and ended up with a 15Kish one. Bought used or dealer demo equipment, made my own room treatments, did much research. Now working towards 25K. As I have a system that truly satisfies, I started my upgrade path with the source. I believe in your situation this approach would serve you well also. In my case I felt the need to get a DAC and transport for CD playback in addition to using MAC computers as servers. I also have a DVD player for movies, however playback is via 2-channel sound only. I not much into multichannel playback for movies as I don't wish to build a theater room. I find 2-channel for movies to be quite satisfactory in my music room. 

I have and still use a Macbook Pro and a MAC Mini as a server and streamer. As a server I rip CDs as AIFF files (equivalent to WAV)  and play back using the Channel D Pure Music program. As a streamer I only have used Pandora or Spotify as I stream to find new music and purchase the CD. I play back CDs via transport and DAC. There are other streaming sources , Tidal and Qobuz are popular, that stream CD quality or higher rez music. I would advise that you research servers and streamers under the digital topic here on AG. I think what you will ultimately want is a server for file playback that also serves to stream. 

My advise to you is to 1st research the use of server/streamers as your primary music source as that seems to be your interest. I would bank most of your 2-3K while researching this and in the meantime purchase a used  budget DAC to play into your Denon AVR. Knowing more about your computer and flies would help here. 

Following that I would get out and listen to as many speaker amp combinations to get a feel for what truly moves you. Keep in mind that speakers play into a room. Pairing them to your room, and treating the room as much as possible to play well with the speakers goes along way towards getting the most out of your system. Following that your amplifier must mate well with your speakers. I would look for speakers that are at least 87dB sensitive and not difficult impedance wise. Another area to research.

Save your money and be positioned to purchase the right product at the right price that fits your predetermined audio scheme. Having an understanding of what your want is paramount to getting it.

Again enjoy your quest. Let's keep the dialog going.

Buy a good turntable and 25 of your favorite albums and you’ll be in analog heaven. 

+100 @mesch who was so helpful as my $9k system went to $13k, but brand new would have cost about $16k because I found a lot of good used deals. The key is to listen and be patient as you learn to hear more. And for the bigger items, such as preamps and amps and speakers, used is very much a good path to go, if you know what you're looking for.

Dadork - here is my 2 cents:

a 10 K budget can go a long way. Your Source is critical - most people under estimate the benefit of a Streamer DAC combined. I have used LUMIN as my source for over 6 years. Very happy with quality and durability- their entry level unit is the LUMIN D2 at $2300.
I use it in my second system - it has to be hard wired to my router for best quality - has the Wolfson DAC - I stream Tidal HiFi with MQA. This source is so good - I retired my turntable.

For amplification - this is dictated by your speaker demands. I push Magnapans - the 1.7i to be specific - and they only cost $2300 new. . I use Krell integrated amps to push both systems but they are expensive (Krell S 550i bought used for $2900 and the new Krell K300i for $7000). The Maggie’s are very inefficient but sound amazing if given enough power. I have enough power. Your speakers are much more efficient - so your power demands are much less stringent. A good used Integrated amp is the way to go - look for one here on Audiogon. Bryston, Marantz (Ruby) and Luxman make great integrateds. A ‘box speaker ‘ I like is made by LSA - I have a set in my bedroom - Living Sound Audio. They can be had used - got mine at $750 for the pair at Audiomart.

my two channel set up works great for my movies, so I have never gone multichannel.

just my two cents!

Happy Listening!