Thanks Dave
IMO I wouldnt get rear speakers but this is up to you.
IMO I would ditch the 6 channel amp for a 2 and a mono amp. If you want to keep the rears get a 4 channel amp and a mono for the sub. This would make it better IMO and have a better and more powerful amp for the sub and have more control and flexibilty for the comps.
If you want some great wiring at decent prices check knukonceptz.co.uk
JL stuff is good but IMO its the sound you are after, with all the better brands they sound different e.g. infinity perfects are super clear and bright, rainbows with silk domed tweeters are smooth and so on.
Also dont order from CAC there has been alot of horror stories and so on. Best bet IMO would be to check out car audio direct. If your placing a decent order you can email them and they might give you 5% off. Also have a much better rep.
As for the sound proofing you can using dynamat but you can get some foilbacked stuff from loudboy on talkaudio or get second skin or damplifier IMO they are better. Make sure you get foiled backed if its going in your doors.
Talk audio is a great place to buy 2ndhand audio but if you want to buy new then CAD seems a better option. Also If I was you I would get MDF rings made for the front speakers. If you are going to sound deaden the door it would be pointless to not have a MDF baffle which mounts the speaker on a thick piece of wood rather than on metal where it will vibrate.
If I was you I would get something like
some dececnt speakers for the front (comps, woofer and tweeter) for about £150-£200. Make sure they are 6.5".
Baffles will be about £20
Wiring will be about £60-£100
If you are only having front speaker get a decent amp, orion, jl, rainbow and so on front only get a 2 channel with about 2x 150RMS so 300wrms for both channels. If you are going 4 channel get about 90wrms per channel.
As for the sub JL's are always a good choice. there are others which are great too. The most important thing with a sub is box size. If you are getting a box it will most likely be sealed as ported needs alot more space. Find out how much cuft volume it needs in the box and pick or get a box built for that size. A proper built box with a crap sub and a rubbish amp will sound better than a good amp connected to a good sub with a poorly built/wrong sized box.
An amp for the sub should be matched roughly for the sub e.g. my sub 10" is 1000wrms and my amp is 1200rms. This gives me some headroom when setting the gain and also gives the amp more damping on the sub IMO. but if your sub is say 200wrms then a mono or 1 channel amp that is 200wrms or even 180wrms will be fine aslong as you are careful with the gains.
That should help you a little