Ya seriously...first of all, there is no way I believe you got that all under 800. What OS are you running? You definitely need a 64 bit OS to use 8 gb of ram, it won't be used at all on anything less. And quad cores? There isn't even a true quad core on the market right now, they are just double duo cores. Do you have a video card at all? Cause a video card to run with those specs would cost another $500 or so, but if you did get all that you might be able to play Crysis or something.
On another note, to whomever said that PCs are still used for businesses but they won't be for long is somewhat incorrect. You also said that if businesses/people will use Firefox/IE then they should have no problem using Safari. This is partially correct. Most businesses won't use Firefox at all, at least not big companies. The reason is because Firefox is open-source and has no real technical support. Most companies will use IE even thought it is an inferior product because it has tech support. You will also never really see anyone move away from a PC in the office of a large company unless they really need a Mac for graphic design or something. PCs are more secure, and they also have the ability to run a MUCH MUCH more secure VPN (virtual private network) and Intranet that Mac's can't do nearly as well. You can't run a large company without either of these two tools because you need the stringent security.
Anyway, that was long haha, but it kinda proves my next point. If you are going to be doing anykind of business or engineering work, I would go with a PC just so you don't lose familiarity with it. Otherwise, if it doesn't matter, a Mac is a great option. One thing to remember is that "Windows 7" the new OS is coming out in 2009 or 2010 and hopefully it will be alot better than vista. Personally, I spent about $1800 bought a Toshiba laptop, 2 GB Ram, 2.87 GHz Duo Core processor, 256 ATI Radeon X1550 graphics card and a few other upgrades. This was about 2 years ago and was a "top of the line" customization but it still can outperform many many computers on the market. Don't go cheap, you'll regret it later.