i Concur with luigipunto.
go to CaraudioSecurity.com
these guyz run a huge outfit, 2 stores in central london, and another one somewere else. One of them is near me. the have a brand new american pick up, with 3 huge solar braric subs behind the driver IN THE SHOP
not to mention a bootfull of ice, and screens everywhere.
to get their best prices, check out Max Power magazine adverts have better offers then thier website, & they tend to beat the competition
check the magazine prices and just give them a call, it cant hurt.
their Labor charges are a bit higher then the cheapest quotes, but its cos they are fully trained & experienced in dealing wit top quality installs.
Aftersales is also good, i've used it, when something broke.
These guys know what they are doing.