iPhone 4 dock

I'm thinking of buying an iPhone 4 dock for 2 reasons:
The dock connector cable has 2 prongs on the edges to hold the cable in place. This might scratch the iPhone. I've looked at the dock and it doesn't have these prongs, probably to make placing and removing the iPhone easier.
Griffin, the company that made my Reveal Etch Graphite, makes a very interesting accessory, the AirCurve.

It's a transparent plastic dock that has a chamber to amplify the sound from your iPhone without any power, like a horn or a record player. Too bad, it doesn't work with the iPhone 4, because the speaker is in a different position. Strangely enough, they want you to use your own dock connector cable with it, instead of making it a real dock. I first saw this on ThinkGeek. ThinkGeek has the odd habit of not mentioning the brands of products, maybe then you won't be able to find them elsewhere and have to buy from them. I had a similar device in the past - a pair of earphones with a box to convert them into a speaker:

I wonder if I could modify it to fit my iPhone. Anyway, I've looked at the dock, and it has holes in the bottom for the iPhone speaker, so it could potentially be modified to this purpose.

The problem is, I looked at the dock today, and it won't fit my iPhone while it's in the case. I can't use it like that. I wonder what other options there are. Do they have extra-long connector docks? Can I use a 3GS dock with a dock adapter? I might buy a dock off eBay, but the quality may be poor and it'll cause more damage to my iPhone.