Dual 23" 1080p monitors (I don't extend my gaming onto the second screen)
AMD Phenom II X4 965 Black CPU
8GB DDR3 (Can't remember specifics)
(Buying a new PSU with GFX card as needed)
Geforce 9800 GT (What I'm replacing)
So first off, I'd like to stick to Nvidia, bit of brand loyalty, and I've never had an issue with their drivers or software, so barring a HUGE difference, Nvidia is all I'm looking at. I've also heard SLI is more consistent than Crossfire.
I'm planning on spending ~$280-300, but can go slightly higher, again if it makes a considerable difference.
1. The first card I seriously am considering is the new MSI GTX 560 Ti 1GB OC Hawk. With possibly purchasing another after the new Nvidia line launches (Sometime early next year?) and run it in SLI. However, I'm seeing a lot of recommendations for more than 1GB when running Dual monitors (Does it matter if I'm not extending my gaming onto the second?)
2. Secondly I'm considering the GTX 570 1.25GB, around $50 more after the 560s rebates, so I'm a bit hesitant, cause I haven't seen any direct comparisions with the new line of OC 560 ti's. ( I don't plan on OC'ing any more than the manufacturer ) Again with the option of getting one for cheaper in the future to SLI. With this I'm not quite sure which card/manufacturer to get either. And if it's a large enough increase in performance to justify the extra $50.
I'm not seriously considering 460s SLI'd, because I feel that doesn't leave room for the additional 560 or 570 I plan on getting in the future.
We all have our preferences and either camp makes great cards.
The recommendations for more RAM apply to higher resolutions for gaming. It's true that your cards are pushing pixels to your second monitor, but since you're playing only on one screen it shouldn't be a huge factor. If you are considering picking up a 3rd monitor down the line and using 3 screens you may want to look for a product with a little more memory.
The 570 is going to be a more powerful card than a 560ti (even the OC'd ones). Additionally, you can bump up the frequencies a bit on any card without changing any voltages- this doesn't require a lot of technical knowledge. However, if you are serious about picking up a 2nd card I'd recommend sticking with the 560ti. You can save the extra cash to put towards the 2nd card or your new PSU. Dual 560ti's are already going to be a very, very fast setup for 1920x1080.