Hey norsey, I bought a x6800 on ebay for $641 shipped and also on ebayt an e6300 with a motherboard for $216 shipped. I have not put together the e6300 system yet, but I can tell you I see people who have slower chips overclocked to higher speeds getting better benchmarks than my extreme edition chip at stock speeds. Also, if you look at this recent review:
http://www.legionhardware.com/document.php?id=618&p=0
you can see that difference between an AMD 3800 and Intel x6800 at settings lower than 1200 x 1024 is nominal. It is mostly video card limited. (wre you gaming?). The difference is even less so between the core 2 processors, which all are at the top of course.
Anyway, shop for that chip, ebay is everywhere no matter where you are. Also, with the first part of your post, you are way better off going with a cheaper processor and getting the newer motherboard. I don't know what king of AGP video card you want to hold on to , but sell it on ebay and go pci-e. You get much higher performance for much less money in PCI-e. The best cards arent even available in AGP. You can use your hard drive in either. DDR II memory is cheaper for the slower stuff. I got 2GB of 800mhz ballistix tracer for $240 after rebate, 2 GB of 677 mhz for $130 on ebay, and 1 GB of 533 mhz off craigs list for $60. I even have one guy on craigs list who wants to trade DDR2 memory for an old socket 478 motherboard. Buy something cheap and new, then upgrade later. Sell off your old crap before it becomes worthless with the passage of time. Sell it to some poor sap who is trying to stretch the life of his dying system and will pay a premium for used parts because they are not manufactureed anymore

. Intel gave a motherboard away with its e6300 chips a while ago. There are a lot of them on ebay for cheap. They retail for $110 an e 6300 goes for $199, and like I said, I got one with my e6300 on ebay for $216 . . . + mem + used case + old hard drive = new core 2 system for $300 if you need to game, insert video card. - Holy cow, I shouldn't drink and post

ending now.