Confused: Should I Upgrade Cables or Amp first?


I currently have very long runs of Audio Art SC-5 speaker cable (about 20 feet) that, due to WAF issues, are routed through holes in the floor, under the house. I use MIT AVT speaker interfaces, in an attempt to compensate for resistance.

Speakers: Silverline 17.5 monitors. Components: modded Jolida JD100 tube cdp and modded Jolida JD302 tube (EL34) integrated. 

I can afford to put $2500 into the system at this point. I could re-route cables through a wall and relocate components into another room, thereby dramatically shortening cable runs to 10-12 feet and enabling bi-wiring. I could also afford to upgrade all cables. OR, I could leave cables alone and upgrade amp.

Which is likely to produce biggest improvement? 
stuartk

I have 22 foot runs of Groneberg Quattro Reference speaker cables that go under the floor in my main rig.  I have never experienced any problems with the sound in the 10 years they have been in the system.  I spoke to the cable manufacturer and was told anything less than 50 feet is a moot point.  I never felt they were hindering my system in any way.

I would look elsewhere to upgrade as you will NOT hear any difference with a shorter speaker cable.

stuartk-

you have a nice, simple system. I would keep the Jadis gear together.
I love cables/cords, and am a "cable" guy first.

Whichever way you go, audition/demo any gear and/or cabling prior to any purchase. Keep me posted and Happy Listening!
stereo5: thank you for your valuable input! I'm expecting delivery of a Parasound Halo Integrated soon from Audio Advisor, so I will focus on amps. 
@jafant , Jadis? Where do you see Jadis? He has Jolida, not Jadis.

I would ask first, what do you feel you are missing?
If you are happy with the sound, then just enjoy the music and spend the money on software, a vacation, or maybe a turntable.
TY- jmc.
Jolida -corrected.

I would like to read more about the modded integrated amp.