Vista - I could use some advice

Hi guys, I am thinking about upgrading my graphics card soon and I'm not too sure which route to go. I have an ASUS P5K-Premium WifiAP motherboard, so I'm all set for SLI. Which is really where my question comes in.
I currently have a GeForce 9800GT, and I'm torn between putting a second one into my configuration in SLI, or purchasing a single, 2xx series Nvidia card. The one I had in mind was a Geforce GTX 275, which is roughly twice the cost of a second 9800GT.
Also, I have a 550W PSU, which should be plenty to keep 2 GPUs, 8GB of RAM, and a Q6600 running.

I appreciate any input here. Thanks!

Unfortunatley, the P5K isn't an SLI motherboard, as it would need an nforce chip. It can only do Crossfire setups i.e. multi ATI GPUs, so unless you upgrade your motherboard, then SLI isn't an option, sorry

A GTX series will still be a great upgrade, though. If the 275's price is your price range, then a GTX260 or 275 would both be a good choice, though I've read and heard the 275 gets a bit too hot when under load.

My two 8800GTS 512s in SLi was recommended a 700w PSU, so you might have been pushing it with a 550w (I rememebr trying a 500w on my 2 and it shut down when under too much load). It *might* be okay for a GTX series card, but don't hold me on that one

hm... i would ditch the nvidia and go for crossfire or a single...... 4870 or 4890 for now and then add a second later

I wouldn't

Pitch the P5K motherboard, spend $200 and get another 9800gt ($99) and an XFX nForce 680i LT SLI Motherboard ($99) or better yet maybe an XFX nForce 750i SLI Extreme motherboard (Also $99). Your system will thank you and you CAN SLI those 9800's. I did and I'm not sorry, check my specs.

depending on which 2 series card your going for it would be better to go that route , first it will be faster and second it will be ALOT less hassle , sli is ok when its working fine but it can be a complete pain in the rear end sometimes

fanboy haha

I've had alot of success with this mobo as far as OCing my cpu (pushed it as far as 3.4ghz while keeping a stable voltage and frequency, though it did get a wee bit warm) and have been enjoying the fact that I can use my PC as a wifi hub for my other wireless devices without the need for a router. There are other upgrades I want to look at before replacing the mobo, but this has given me somethign to think about when the time comes.
(I'm kind of kicking myself over the crossfire/sli thing...) Does anyone have any suggestions of a pair of ATI cards that might be comparable to a single GTX275, without breaking the bank?
Thank you very much to everyone who replied to my thread, and for pointing out my blunder Everlong18

With only a 550w PSU, a pair of 4850's are probably a good option. Performance wise, it's roughly equivalent to a GTX 285.

I like the look of those 4850s... Having one would be a step up from my 9800GT, and then adding a second one later would not be a big expense. and even then, the two of them are cheaper than one GTX285
How do 4850s like being overclocked? Does anyone have any experience with these cards?