Can't show off something if it's broken. can you?
iMacs.... depends on personal preference, some people thinks Apple Products are overpriced POS, many thing they're god's gift to Macnians (i made that up) with shiny interface.
I'll probably get flamed for saying anything against Apple, but what the heck, Don't get iMac, let's be honest here, OS TEN has very limited support in terms of hardware and software. iMacs have the keyboard built into the chassis so even a little spill means the white thing will die. get either Dell or HP. Sorry but just because you add a "i" to everything you sell and paint it in Blindingly white or grey doesn't mean you get the rights to charge heaven and earth for it.
as far DX10 Cards in Laptops are concerned. you need to realize that at a budget of $1,000 you'll only get a entry level DX10 Card (8400GS prolly), No practical use considering there no DX10 games available and those who are (LP: EC, CoJ, CoH v1.7) Make even the 8800GTX and 8800Ultra Crawl. DX10 is quite simply too immature right now, the technology is new and hence will take some time, it's never a wise idea to be a early adopter unless you have money to waste. besides, last time i checked, No DX10 Laptops were available (please correct me if i am wrong) Entry Level Laptops with DX9 are not for today's games anyway. if you want to buy a laptop to play current gen games, you won't get it in $1,000. ASUS and iBuyPower have some nice Gaming laptops though.