Where should I route my amp's power wire into the cab?

[71ChevySS(straight6)]

I got some 4-gauge welding cable to use as power for my amp, have some for my ground cable too. The question is, where do I route the darn stuff into the cab at?

Also, what do you guys recommend I do? Here's my situation:

-I leave for college in three weeks.
-my truck is currently non-running condition, with at least four good days of work to be done on it (motor needs finished putting back together, 250, front header doesn't fit properly; need to install an exhaust system; then I need to make it road-legal, blinkers don't currently work, need to replace signal switch support, gonna do that this evening; exterior door handles need replaced)

but I've wanted to have some thump in my cab for the last four years I have a Sundown SA-8 V1.5 and an old-school 500-watt-max Bazooka amp. I'm considering just throwing together an mdf box to ride shotgun on the middle of the bench and fire up just temporarily, til I can relocate the gas tank and build a proper box. I can set it on the floorboard if I need the bench, or I can take the whole thing out and put it in my toolbox for a little while.

Or, should I just take the time and spend the money right now to put it behind the seat?

My college is freakin' expensive. Keep that in mind.