Subwoofer placement questions

In my current system, I have Spica TC-60's sitting on top of Audio Concept Sub one passive subwoofers. When listening, I pull the speakers well out into the room. I know this set up is not ideal for either the Spica's or the subs. If I purchase stands to put the Spica's on, I would need to move the subs out of the way to appease the wife's decorating. One sub would end up next to the computer desk on the long side of the wall. The other sub would end up in the corner next to the couch used when listening. In this set up, I will need approximately twice as long of speaker cable (25' vs 12') for the subs compared with the Spica's. I would expect more bass by having corner and wall support for the subs. I would expect better imaging and soundstaging from the Spica's by having them isolated from the subs. However, won't the difference in speaker cable length cause timing problems ruining the systems "prat"? Musical preference is varied from 70's rock/pop to country to female vocals and jazz and blues.

For info my system is:
Music Hall MMF-5 turntable
Music Hall CD25 cd player
Kenwood KT8005 tuner
C-J PV10A preamp
Musical Fidelity A3cr amp to Spica's
Carver TFM15 amp to subs
Homegrown audio super silver/silver lace ic's
audioquest Crystal bi wire spker cable to Spica's
Audioquest type 6 cable to subs.

Any suggestions are appreciated.
The signal travels down the speaker wire at at least 650,000,000 feet per second. I figured 2/3 the speed of light but it may be faster depending on your cables. It would take the signal about 20 nanoseconds (.00000002 seconds) to travel the extra 13 feet at that speed.

On the other hand, sound travels through the air at about 1100 feet per second. That same 20 nanoseconds difference would be equivalent to moving the speaker 22 microns (.000022 inches.) So I think it is not an issue.

I would be more concerned with the asymetrical placement of the subs. This will cause them to be reinforced differently. One could then have significantly more output at some frequencies than the other. Their outputs also combine with each other and with the lower frequencies from the monitors. So having them at different distances can cause them to be additive at some frequencies and subtractive at others.

Without the aid of some rather sophisticated computer modeling I think your best bet is to just try it.
The length of the wire doesn't affect the signal timing at all; it travels at the speed of light. So don't worry about that. The more important thing is if there is a path length difference between speakers-to-ears and subs-to-ears. That will affect signal phasing and if bad enough will also affect frequency response in the crossover region. So try to keep the path lengths more or less the same and you will be in good shape.
Since I have a spreadsheet open (taking a break from work), I'll put Karls' comments in perspective. The electronic signal would arrive at the sub-woofer about 2 one hundred millionths of a second later than your mains for an added 20 foot run. Much less time than mere humans can notice. However, a twenty foot difference in distance means about 2 hundredths of a second lag acoustically -- i.e., from the speakers to your ears at the speed of sound in air. That may be noticeable -- ears are pretty keen regarding distance and direction.

If it is noticeable to you, keeping the distance difference to a few feet could help. A bigger concern might be directionality. Depending on how you set the cross-over on your subs, location will not be directional. That should help in the set-up. If the sub reproduces sound above 100 - 140 Hz, you also need to worry about directionality and that means you need to place the subs near the mains. Otherwise, you only need to (as Karls recommends) worry about the relative lengths of the signal paths to the listening position. Good luck.
Your biggest concerns will be how they are loading the room(placement) and phase. Dont think you will hear "lag time".