http://cgi.ebay.co.uk/Stinger-SBASS4-Ba ... 5884b729b1something like these H will sort you out a little. I used to run my headunit on -2 bass +4 treble, loud but with a heavy bass from the sub adjusted by the amp. If your HU has 2 pre outs its easier as you can tune the sub and speakers off the HU. mines doesnt in Jeremy so i play with the amp instead and adjust levels. Jeremy needs setting up abit better but vans are the devil for sound... so much air to move and much more rattle.