Pricerunner is about the best one, but its still not brilliant for hi-fi/home cinema stuff.
Richer sounds are great for the lower end of the market. Superfi are a good on-line outlet. The more specialist higher end stuff tends to be only available at specialist hi-fi / home cinema dealers and isnt generally advertised.
Google is as good as anything.
As Big A says calling shops takes time but can reap dividends.
Pioneer KRP-600A, Pioneer LX08, Pioneer SC-LX81, Sky HD+, Tannoy Revolution Signature DC6T, DC6LCR, Arena Highline 500 Rears, Sunfire HRS-12 Sub, Chord Silver Plus HDMI & Chord Rumour Speaker Cables, Clearer Audio Mains Cables, AV Podium Rack