Like to tweak my system

I'm fairly new here and just learning.  I have a Yamaha R803 and Vandersteen model 1s.  I stream Spotify. I'm happy with that for now but I'd like to improve the sound in other ways if possible. I previously asked about better speaker wire. Perhaps a power conditioner, DAC, amarra software, a better power strip?  Any recommendations would be greatly appreciated. BTW, as recommended here I purchased Jim Smith's book, great advice, thanks.  Doug
With your current system your not going to get any "aha"moments with tweaks like power strips.
Is the room acoustics sorted out?You want early reflection points treated and check for room echo(walk around hands above head clapping loudly-you will hear it if it's there).Balance hard reflective surfaces with curtains,rugs & wall hangings..Also if you have a big tv in between the speakers get a good blanket to cover when listening,it will increase soundstage depth and height.
The Vandersteens are time aligned so they need to be perfectly aligned both horizontally & vertically.Use a bubble level for set up..
40' speaker cables?That's a LONG run,generally you want speaker cables as short as possible.Better to use a longer run of good Pro Grade USB cable...
 If you REALLY want to hear those 1C's sing add TUBES!A decent 40wpc.EL34 amp.will put you on another level with those speakers.
Okay so here's what you do: spend as much time as you can listening to as many different things as you can in as many different stores as you can find.

But that doesn't mean 100 systems in 50 stores. Lotta guys do this, learn next to nothing. What you do instead, every place you go, you listen to one system and then you listen to it some more after they have changed one thing. One interconnect. One power cord. One CD player. One thing.

Then you make note of everything in the system, or at least as much as you can. Eventually you are gonna be looking and asking and making note of things like was that left on overnight and if not then how long was it turned on before I got here? Because it matters. A lot. In the beginning though you got your work cut out just keeping track of the big stuff.

When you get to the point you're seriously considering buying something, bring it home first. Not just the one you're considering either but at least one other contender. No exceptions. Not in the beginning. Eventually, many years from now, you may reach a point where you feel confident enough in your detailed understanding of how each component works, how to read reviews and which reviewers to trust, to buy a thing or two unheard. But for now the rule should be, audition first.

This is a lot of work. So much work, hardly anyone ever does it. That's why almost all the advice you will get is buy this or buy that. Buying is easy. Listening is hard. But totally worth it.
Thanks for that advice, I really do appreciate it.  Doug
Something to try and keep in mind, its the little details of setup and tweaks that can make the difference between a really cheap system that sings and a really expensive system that sucks. I haven't read the Jim Smith book, my pick would be Robert Harley's Complete Guide to High End Audio, but I gather that is pretty much his theme. If its not it should be.

The most captivating system I ever built was $1200. Speakers, integrated, CDP, interconnect, speaker cables, power cords, cones under everything. All-in, $1200. Done for my father in law, set up in my listening room to burn-in, sounded so good I listened to it every chance I could until it had to come out to go to his place. 

The Vandersteen Model 1 you have is very well regarded. But you're driving it with a receiver. When you go out and compare, I think you will be surprised how awful just about every receiver sounds compared to just about any integrated amp. But same goes for the lamp cord, patch cords, and power cord they throw in the box for free. Which you are probably using. Which of these to tackle first is something that is probably a puzzle now, that will seem to solve itself at some point when you've compared enough. For now pat yourself on the back for having a really nice pair of speakers. Most guys never get even one good component early on, so you got that going for you. 
That's good advice, thanks. I have an audiophile friend who told me that over the years he probably spent $50k on stereo equipment by buying, selling, trading, upgrading, etc. He said if he could start all over today, he could put together an equal system for about $10K.  He had fun and has no real regrets but the advice he passed on to me was.... take your time, learn first, then choose wisely.  I have a nice system now (Yamaha & Vandersteens) but have felt tempted to upgrade when I see better equipment but so far managed to hold off and keep learning. Usually the next day I'm a bit relieved. I'm sure I'll upgrade at some point but hopefully I'll do it smart.  Although that little MAC MA252 has been calling my name!
A quality recording on CD will greatly surpass the sonics one gets from Spotify. I use Spotify for finding new music to purchase, playback is accomplished via transport or computer file derived from CD.  
+1 for Jim Smith's book. 
Get your setup dialed in.
Do room treatment.
You now have done half (or more) of the battle.
Now focus on better gear.