1) your 600w is actually a 400w PSU and i wouldn't even run at that level for fear of a spark show.
2) luckily the 9800GT will hardly draw much power so you shouldn't even break 225w total system power while gaming with most CPUs. so to answer your former question, yes it will work but your PUS is still mediocre at best.
3) to asnwer your later question, no one can give you recommendation on a PSU without first posting the make and model of the PSU. there are no regulations for PSU market so I can take your Orion 600w PSU, place a sticker on it for a dual split on the 12v rail for 25a each and you would never know what it can or can't until its too late. that is why independent test for PSU are so important.