And Sextons.............. 
I'll agree with that, well at least my local branch, not the on that Dizzie works at

know what I mean Gaz!
I take it that my system was a bit £Â£ then Tim? I personally would recommend a 10" JL sub, as they seem to be (in my experience) bloody awesome, and if you're a 'rock head' then a 10" will suit your ears a treat, but still allowing you to manipulate the sub under dance music conditions.
What head unit are you using, as this also can be the deciding factor? If you're using an old headunit without a sub out then it makes it difficult to change the subwoofer settings, but not entirely impossible as some kenwood amps come with a remote level control. It may be prudent to speak to Dizzie, see if he can point you in the right direction, and the best combination for your money.
Lewy