Come on now, you can't go in without a plan. It really sounds like your trying to throw this together with some duck tape. No that I'm finish with my rip, take this into consideration. First What type of box are you going to use, not all are equal, ported, sealed....
Secondly, what locations have you though of this far; and I do understand that you are looking for ideas, but give us yours to see how much help you'll need.
Third, what type of trac do you have, and what type of system, after market, Adrenaline System, premium, etc and if so, do you have a factory sub in the back, now what you could do if you have a factory sub, is tape into the 4 wires that go into it, (red, blue, white, black, I think) then get your self a T tap so you do screw up the factory wires by cutting them, or cut them and use a connector so it "splices into the factory cables". Whatever you do, your next step is to get a converter, wire to RCA if your patching your cables.
The only real space you have is under the bench, now if your box is to big, it will not fit, if you have custom, it should fit like a glove, check ebay, they have boxes for 10" for trac's.
MAKE SURE YOU GROUND THE CONVERTER AND THE AMPS GROUND TO THE SAME AREA, NO OTHER OPTION unless you want crap (feed back). I can say this because I did it a lived with it not knowing, so take it from someone who has been there.
Last, get yourself an amp. There are many to choose from but if you are going to run a pair, then get yourself something that is at least a 2 channel. now the wiring is really simple. If your 8"'s have a double coil, then I would suggest crossing the from one wire to the other magnet on the same sub. http://crutchfield.custhelp.com/rnt/rnw/img/enduser/2Ch_2-2ODVC.jpg
or http://crutchfield.custhelp.com/rnt/rnw/img/enduser/Mono_2-2ODVC.jpg take a look at these for a loose reference.
Then install your system and try not to make your ears bleed.
