Best improvement for the buck


I just recently sold a McIntosh mc250 and now have about $900 to spend to improve my system. 
Parasound p5 
Parasound A21 +
Denon dp51f  with grado gold
Magnapan 1.7i 
Klipsch 10" sub on stand
Oppo bdp83 
Blue Jean interconnects 
Sony 8" sub on stand
Monoprice xlp interconnects 
DIY braided speaker cable. 
So now the question is what is the most logical improvement or improvements.any suggestions?
audiomaze
@audiomaze ...

If your looking for quality cables at a reasonable price, give Grover a call. I've heard his latest cables at the homes of friends and found them to be impressive.  http://www.groverhuffman.com/home

Frank
Consider upgrading your speaker cables. I would advise trying the Alpha Core Goertz MI 3 Divinity Bi-Wire. Goertz has had a known synergy with Magnepan. The Cable Company has a 30 day return policy. A stand alone tube phono preamp like an Allnic H 1200(own one) would bring your viinyl to another level. I do agree room treatments are a must but IMO have your system dialed in then the room treatments should be more effective.
I'm with @erik_squires  -- especially about the chance to improve the DAC in that Parasound P5. You have a lot of nice options at $900.
You could explore variety in obtaining a second, different type of speaker to have a contrast. It's a great way to play the game.  

Obviously, you can upgrade your sound with the speakers you have, or new ones, but as an option to hear more variety, a second speaker, such as a horn hybrid, is a terrifically fun way to go. Imo, there are not many things in the hobby more fun than swapping out a speaker and having a "new" rig, a new sound at your whim.  :)