This is what I have put just behind the seat.
£140 on eBay, £180 in the shops
In Phase USW10 features
* Maximum Power Output 300W
* Rated Power Uotput 100W
* Output Impedance 4 Ohm + 4 Ohm
* Crossover Frequency 50-100Hz
* Size: 270mm (diameter), 69mm (height)
* Weight (inc accessories) 4.8kg
* Phase Button (0-180 degrees)
* Remote level Control (5m)
* Aluminium Cone
* Ultra Slim Design
* Die Cast Aluminium Chassis
