99.9% of the time the power supplies that come with a case are garbage. even if they do supply enough power where it counts, chances are it won't be good, clean power.
With a C2Q and a 9800 you will be fine with any quality 500 watt PSU. look at 500w PSU's with either a 30-35A 12v rail, or dual 20-24a 12v rails (2 x 22A 12v rails will give you about 32A total with 12v). Those 2 components probably draw ~10A on the 12v rail, each. That is 240 watts right there.
If you give us an idea of your budget then maybe some specific PSU's could be mentioned. i.e. a quality 500w PSU will cost the same as an adequate 700w. you might consider adding in several new hard drives. in that case the 700w might be better.
Something from Enermax, PC Power and cooling, Antec, OCZ, Seasonic, Fortron/Sparkle, Corsair are usually a good unit. (
HERE is a very comprehensive list-probably TMI, but interesting if you are interested in computers--you can pretty much look at PSU's at a store like Newegg and then search in that thread for it and see where it stands)
When it comes to PSU's, its not the watts, its the amps you are interested in. in many cases a quality 500w power supply will be better than a cheapo 800w for your application because it has the same or higher amperage where you need it. There is a lot of marketing jargin you have to see through to tell if the PSU you are looking at is really good, with the exception of a reputable company. Some PSU's are rated by the MAX output, which is not the same as what they can continuously put out 24/7. Chances are a correct PSU for your hardware is also more efficient and you will not be wasting power. if you go out and buy a 1kw PSU that says its 85% efficient, it is probably only 85% efficient when it outputs around 750-850 watts. at 350-400 watts it might only be 60% efficient (there aren't exact numbers, just a ballpark example). this means that to get 400 watts to computer components you are drawing 650+watts at the wall. If you had a 600watt PSU that is 80%+ efficient around 400 watts you would only be drawing 500w from the wall. the efficiency rating is how effectively power is converted from Ac to DC. Also, power supplies lose a certain percentage of their output every year just from wearing out. Most will lose 5-10% of their power output per year, so buying the bare minimum might not work out in a couple years.