what else do i need to improve sonic performance?

do the power cables, you will not believe the difference!

This is almost universally agreed on.

When I changed out the stock PCs in my system the sound opened up to an unbelievable degree.

DIY VenHaus is a good cheap start

also Pangea Audio gets a few positive nods around here.

good luck and have fun

I agree with Philjolet. Just one word of advice...components with a low current draw such as a preamp do not need the heaviest gauge PCs.
For example, Pangea sells the AC-9 for amps and the AC-14 for preamps, CDPs, etc.
I also suggest you research the different types of power conditioners. With cleaner power, you will hear an improvement.

i own the pwd. while it "reads" 24 bit discs, it is an unremarkable component for 16 bit cds. Consider a replacement, unless you listen exclusively to hi resolution files or reference recordings dvds.

People can suggest quite a number of things that in their opinion may improve sonic performance. However, you left out key details. for example, what is really missing in your opinion from your system's sound? Are you in Heaven when you sit and listen and never want to get up? or is something(s) missing? and if so, what? lack of depth, dimension, accuracy? too bassy? no mid bass or highs? What is your listening room like? many times the room itself can really negatively impact the sound. Simply suggesting equipment may not help if one doesn't isolate the real problems. for me, I need to really address the room itself with people knowledgeable in that area. Do you have friends knowledgeble in audio, music and equipment? that can come by and listen and offer opinions?

enjoy