whats more important-speaker or pre-amp cable?

IMHO, the affect of a long run of IC is likely to be less audible than a long run of speaker cable so long as your pre-amp can drive a long run. A long run of speaker cable is more likely to result in rolled off highs and softened bass response. Personally I would go for the long IC and short speaker cable, everything else being equal, but I have successfully used 20ft runs of Canare Star Quad 4S11 speaker cable and short Blue Jeans LC-1 IC's with excellent results, especially considering the nominal expense involved ($35 for the IC's, $65 to $75 for 20ft runs of cable). It is, I think, a great place for the budget constrained audiophile to begin. Some might even end there. :-) BTW, I think the speaker cable is the best part of the deal, but the IC is pretty good as well. Some might think it is a tad soft in the highs, but if your stuff is a tad bright, it could be a perfect match. In any event it doesn't get cheaper.

I second Newbee' good advice.

+2 Newbee

Better to have a long speaker cable as the interconnect is carrying a more sensitive signal.

My experience has always been to keep the ic's short as possible and of good quality. Longer speaker runs will generally result in a loss of gain but the frequency response will remain intact, again using good quality runs.
As Argyro said, the ic's are carrying a more sensitive signal.
How far apart are your speakers going to be that you need 25ft speaker runs? You must keep the speaker runs the same length, I'm sure you know.