That is an old style PSU with only 17A on the 12v rail. You should definitely get a modern quality PSU. The monitor plugs into the wall and won't affect power draw on the PSU.
Save up a few more $ and get a new PCI express rig - don't waste monry on old tech
Your Allied PSU is cr@p. Get a REAL PSU like a Corsair or a PC Power & Cooling.
It only has 17A on the 12v Rail. You might be able to run run it, depending on the power draw of your other components, but that could be pushing the power supply and the load on that rail could cause it to fail sooner rather than latter. Newer power supplies will generally have more Amps on the 12v rail and less on the 5v and 3v rails. I think you may be better off going with a 3650 AGP as you will generally be CPU limited with a 3850.
If you go with the 3850 then try running 3D Mark. If you hear a high pitched wine at anytime turn off the system IMMEDIATELY. Just flip that power switch on that surge protector because that's the sound of your PSU crying out in pain ^_^. In that event I would recommend investing in a good high quality PSU that you can make part of your next build.
Thank you so much for your responses. After reading the posts ive decided that a 2600xt would go good with my system considering it does not draw as much power. Im trying to make my system match that of an xbox 360 so i can enjoy games like dead space, lost planet and mirrors edge w/ out spending 300$ to get an actual 360.
2600XT ain't going to cut it imo.
well considering my system specs. (Im not going to upgrade my PSU) do you know what would work best. maybe 3650? Thanks