What Graphics Card for Newly Built Gaming PC?

Yeah a 4890 is a good choice and it overclocks well. It won't max out Crysis at certain resolutions but it will for the smaller ones. What resolution screen to you plan to play on. If you've got a big screen your only choice is a dual-gpu solution for maxing it out. I think you only have 1 PCI-E slot (just a guess) so you could get a 4870x2 or a GTX295, if you have the money.

To play crysis at very high settings you would need something like a 4870x2, gtx295, or a crossfire/sli rig to even approach playable frame rates. You would also need to substantially overclock the cpu.

For everything else a 4890/275 would be fine.. though that depends what resolution you like to play at.

I must question the choice of a slow quad core CPU though, when games get the multi threading support in the future it may perform better than a dual core.. but as far as a budget system goes a fast dual core would have been a better choice. Of course you can always overclock the CPU.

^ Do not mock the afflicted.

What resolution is the new monitor you plan on buying?

man you need a new monitor badly, 1280 x 720 ouch. Shop around you can get the standard in gaming now (24" ) 1920 x 1200 for less than $300. The 4890 is a good choice but the 5000 series( Direct X11) is just around the corner from ATI I would wait and see another month or so.

OC your Q8200 to about 2.7GHZ and then buy yourself a HD 4890 or GTX 275

'a 650w PSU'...

How about 'this 650w PSU'? Not all PSU's are created equal. I'd give a rosewill 650 to someone that I didn't like, but I'd have to really not like them...

For your current mnitor, go for a 4850/4770/9800GT/GTS 250. Rest is awaste of money and resources.

If you plan to upgrade your monitor on the same card, then go for 4870 1GB/4890/GTX 260/GTX275.
Also, keep in mind that the DX 11 cards are rumored to be here by October ( thats the time when all the major games release- call of duty MC 2, NFS, Assassins creed 2 etc). A $150 DX11 card would easily beat all the above mentioned cards in DX11 games, but not at DX10 Games.

So, tread carefully on the path you choose henceforth....lol... Kidding....

^ Most games, but not Crysis

Get a 4890, OC your CPU and be happy. You will be able to run Crysis on High at that res, most likely anyway. If you want to raise your settings to very high at least lower some of the more CPU intensive options to high or medium to prevent your CPU from bottlenecking your GPU as much.

I stand corrected, O Bling Master!