It depends... There are several things we need to know and you need to check:
1 - What you are using the card for?
For basic computing, media creation (ie mp3's, DVD, etc) and older games it should be fine. It should even run some of the newer games but not at the best resolutions or quality. I have the 8600 GT on my laptop and it works fine for how I use my laptop. However if you plan on playing any modern games I'd recommend at least an 8800GT or a 9800GT. I've read the 8800 GT is actually a better card than the 9800GT (and the 9800GT is better that any 9600 card) and it is what I purchased for my desktop. I got my EVGA 8800GT from Newegg for $99 after rebate but they seem to be in short supply lately. BTW, here is a link comparing the 8800GT to the 9600GSO: http://www.tipidpc.com/viewtopic.php?tid=147591&page=1
. Not many comparisons or reviews of the GSO just yet.
2 - What case is the card going in?
You have to make sure the card fits. These new cards are very long and a tight fit in most mid-tower cases. My 8800 GT juuuusssst fits on my Antec case. You say you have a "Dell XPS 600 sli mobo". Is it still in the Dell XPS 600 case? If so, you should be fine as these are fairly large cases. If not, check the clearance you have and make sure you have an additional 1/2" or so for the power adaptor required for the card. With the 1/2" things will be tight but it should fit. Also realize that this card is double wide and will block the slot next to the PCI-e slot. Make sure it's not occupied.
3 - What kind of power supply do you have?
New cards tend to be very picky about the voltage. This card requires a power supply with a minimum 12v current rating of 26A. Very few older power supplies meet this requirement. Does the power supply have the required 6 pin connector? If not, the card comes with a splitter that you can use if you have 2 available Molex connectors.
Before I purchased my card, I did a ton of reading about the different cards available and the requirements for the ones I was interested in. You should do the same.
Finally, make sure you check the return policy just in case you have any issues. Newegg hasn't been as generous as it's been in the past. If fact, the card you link to is non-refundable. You can only exchange for the same within 30 days if it is defective. I try to avoid deals like that.
PS - If you think this is the card for you, Newegg has and additional discount code (EMCBACECB) for $10 off. Good until 10/30/08. You can find the code at this link: http://promotions.newegg.com/NEemail/latest/index-landing.html
Good luck and let us know what you decide