VS Ute Sound Systems. this might be a lil help.
I've got slimline subwoofers behind each seat. Been looking at getting newer subbies though. Dunno if you have seen them on eBay but you can get slimline subwoofers with a built in amp with remote for $200 each. No idea if they are any good but they are specially designed for utes etc that dont have much room.NEW TITAN AUDIO SLIMLINE ACTIVE UTE SUBWOOFER - 400WATT - eBay Subwoofers, Audio, Video, Car Parts, Accessories, Cars, Bikes, Boats. (end time 06-Sep-10 19:59:45 AEST)
Run my speakers of my head unit and 2 woofers off my amp. Last thing you wanna do is go and buy a new amp if you've already got a decent one.