i7 or only quad worth your $180 is OEM Q6600 with G0 stepping.
Here's what I would build right now, especially with recent price drops:
Processor
Q9550
$229.97
- equivalent to most expensive Quad extreme on market
- overclockable like a motherfucker
- 12Mb (highest) cache
http://www.tigerdirect.ca/applications/SearchTools/item-details.asp?EdpNo=3952342&CatId=2758
Motherboard
EVGA 780i
$145.99
- 3 PCIe 2.0 x 16 slots
- up to 8Gb DDR2 1200Mhz (more then you'll ever use/need)
- all other fantastic, future-proof connections on it
http://www.tigerdirect.ca/applications/SearchTools/item-details.asp?EdpNo=4349462&CatId=3495
RAM
OCZ Reaper
$138.99
- 4Gb (2 sticks of 2Gb each) 1066Mhz RAM
http://www.tigerdirect.ca/applications/SearchTools/item-details.asp?EdpNo=4350424&CatId=3413
Case
Cooler Master
$149.99
- HAS 932 case
- huge 230mm intake fan
- side 230mm side intake fan
- top 230mm exhaust fan
- rear 140mm exhaust fan (all included, and they're HUGE = quiet)
- can accomodate TWO (no joke), TWO powersupplies
- water-cooling (thinking future here) ready
- has room for whatever the fuck you throw in there...amazing
- a NASTY, NASTY CASE!
http://www.tigerdirect.ca/applications/SearchTools/item-details.asp?EdpNo=4146085&Sku=C283-1187
$1329 before taxes... I know it's SLIGHTLY above your stated budget, and it leaves you without a Power Supply (however, yours right now running your current vid card, you're fine), and a proper CPU cooler, you can pick up a CPU cooler for about ~$40-50.
This is a SICK system, and I'm only assuming you need everything listed. Don't be afraid to purchase some main parts and mix with what you've got now... save up a bit more, and buy the rest. DO NOT CHEAP OUT on:
- Motherboard (upgrading this, SUCKS), so buy good from the start
- CPU - same reasons as above
You can still use your current hard drive and operating System. You can always upgrade to Win 7 whenever you want, hell, I'll burn you my very same install DVD I download, and it's working PERFECTLY... God knows I live 10 mins from you...
Enjoy :)
EDIT: One last thing, I can almost safely assume you already have at least 2GB DDR2 RAM in your current system. You don't have to buy the OCZ RAM now, use your current RAM and save almost $200, making this system right in your price range... upgrading RAM is simple as fuck, and RAM is the least impacting performance part in your whole computer - with the exception of RAM from the early 90's.