I love you Skip, you're talking my lingo here, lemme throw a couple of solutions at you.
First off, your case constrains are brutal, and finding a desktop or HTPC style case at only 4.5" tall is gonna be one hell of a tall order. Here's an idea of what you're looking for however:
NewEgg HTPC cases, the shortest ones are the Apevia models at I think it was 5.4" tall, but I suspect things will be supremely cramped. Either way, you're going to have look into giving this more room, especially to breathe.
PSUs are pretty much a dime a dozen, but I will say if you're going for quiet, SilverStone with a 120 or 140mm cooling fan will work perfectly as it'll be quiet and deliver the juice you need consistently (I've used SilverStone twice with fantastic results until I popped them myself with bad installs). Do not go for anything with an 80mm fan no matter how slow it spins, I cannot stress that enough.
If you're seeking just a Blu-Ray drive for reading purposes, brands to look at are specifically Toshiba and Sony (the creator of the format, and the former it's competitor with HD-DVD). Burners are whole 'nother realm that I have not dove too far into so I can't comment openly there.
RAM is easy.
AMD Radeon DDR3-1600 16gb (2x8gb) is a perfect compliment.
I just recently built an A8 for a friend of mine with all AMD components like you're going here (A8, D3, and AMD-R ram), and she had no problems with compatibility, performance is top notch for the specs that she's got, and she couldn't be happier. She's coming from years of laptops so talking her into getting an actual PC that doesn't move around was a feat, but I was more than happy to help her pick out the machine for budget pricing. Overall she spent less than $500 total for the setup and it should last her another year or two before it's too depreciated for new games.