Try Bell and Elephant too. Again a bit mainstream maybe but if you don't mind not having agreed value then they're worth a look - I was with Bell for about 3 years at £ 500 with no mileage restriction and they were very good (I was about 25 at the time I guess). Now I use a broker for agreed value.
With Bell it was best to talk to them and play them off against the cheapest in the normal way.
Elephant seem to use the same 'engine' to generate the quote - same questions and web interface when I last looked. Elephant was a few quid different but had an additional section where you could make allowances for mods and was very easy to tinker with on their web-site. It was fun seeing how much a modified exhaust, chip etc changed things.
Of course no two alpines are identical really (so many minor variations by now), and those Devil Exhausts could be ordered from the factory as 'standard' so not really modified is it
....... and as for that K&N filter, well see Homer Simpsons advice number 3.
Homer to Bart:
"The three little sentences that will get you through life:
One. Cover for me.
Two. Oh, good idea, Boss!
Three. It was like that when I got here."