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
When I was young, I'd place a penny on the head shell when it went over a skip on the record..... really!
Depending on who you ask the correct answer is "room treatments" or "sell all your gear and buy a Raven integrated and a pair of Tektons".

Don't be silly. Depending on who you ask the correct answer is "GIK" and "How NOT to buy a subwoofer" or something that actually makes sense.

Although I must admit a Raven would be a vast improvement.

Well actually I'm looking at all Raven cables which would wipe out my stash but might be a game changer.