I'll look up some specific hardware for you when I get a chance but first some general suggestions.
An i5 will last you for quite a while. I don't believe there is a game out there that benefits from more than 4 cores. So a high end i7 won't be necessary. The new Haswell i3/5/7 line should be out by the time you have the cash. I would recommend those as they are more power efficient with all the benefits of the previous chips.
This is going to require a brand new motherboard. I say prepare for around $400 for a mobo/cpu/ram set. Maybe a bit more as, if I'm not mistaken, smaller motherboards tend to cost a bit more than fuller sized ones. You should be fine with a mATX mobo but don't go Mini or smaller. They will not have room for your regular PCI cards like your sound card.
For a graphics card, a GTX 650Ti Boost will be a big jump for you over the 460 while keeping costs low for you. They run around $180 on Newegg. On the AMD side I would recommend the 7790 as it also has a good price/performance ratio in the same price range. They tend to run around $150. Now if you're willing to spend a bit more and want a smaller form factor for your LAN rig, I suggest taking a look at this card from ASUS.
ASUS Mini-ITX GTX 670
I kind of want one because it looks pretty cool to me. It hasn't been priced yet, nor have they released a date for it but it will probably cost a tad more than a regular 670. So expect around $500.
An SSD should help a lot with load times but you will most likely not benefit from it for mulitplayer LAN sessions. So that one is up to you. Your Velociraptor should be plenty for you until you save enough for later, if you decide to go that route.
Your current power supply is more than enough for a single graphics card, a new Haswell Intel chip and all your other necessary peripherals.
Regarding the OS. You can always get Windows 7. That's 64-bit and I believe cheaper as well. Windows 8 is fine too if you want to just jump to the latest. It is a better version of Windows 7 with that crazy metro interface. So if you have the cash, Windows 8 is perfectly fine for gaming.
That's all for now. I can give you more specific suggestions if you like when I get a chance.