Ram isn't really an issue as the ATI cards up to full native 30' resolution don't need more than 1GB of video ram in general. Even 1GB is overkill on some cards. What you have to look at is the speed and type of the ram on your video card. Obviously GDDR5 at 950MHz (3.9Gbps) like the RV790 (i.e. 4890) is extremely fast. Alongside the 256-bit memory interface you really don't need more than 1GB of video ram; just like the new AMD AM3 processors that don't need more than 4GB for all needs, other than video editing, CAD etc. The added throughput and higher clock speed of DDR3 over DDR2 allows you to use less ram. Even 2GB of DDR3 will play almost all games no prob. Ram on video cards work the same way.
If you can I'd wait a bit before buying a new card.
If not buy two 4890s, although the 4890X2 will be the way to go (
http://www.tomshardware.com/news/amd...hics,7531.html) and it's supposed to launch soon so...
Generally two 1GB 4870s in CrossfireX are on par with a 4870X2. In fact they run cooler than the single X2 keeping your ambient case temperatures around. The 4890 is built on 55nm architecture (that's the RV790 specs); the 4770 is based on the 40nm RV740 chip. In percentage terms you will have more overclock headroom on the 4770 than the 4890s and 4870s. As the 4770 was just launched, the next range of ATI cards will probably also utilise 40nm architecture. In fact two Crossfired 4770s (512MB) outperform a single 4890 (1GB) (
http://www.tomshardware.com/reviews/...fire,2288.html) proving the 40nm architecture is the way to go.
In terms of the debate between, for instance, a single 4870X2 2GB vs two Crossfired 4870s 1GB they are on par in terms of everything really: power utilisation, performance etc. (
ATI Radeon HD 4870 X2 Performance Preview and
Pair of 4870s VS single 4870X2). As money is not an issue for you then the 4870X2 is the way to go. I have to mention though that the Sapphire HD4870X2 is really cheap at the moment so you can get two for about US$150 more than a single of the other brands. Two 4870X2s would be insane! Although I remember reading somewhere that 4 4870s Crossfired can keep up with 2 4870X2s at anything on or below 1680 x 1050 resolution so...2 4890 Crossfired have the same issue at higher resolutions as 2 4870s.
The 4870X2 however has some link between the two memory chips and I think processors that can be activated via software, i.e. Catalyst drivers. However ATI hasn't yet released these. Basically it will allow the two separate processors, memory interfaces to run as one. Effectively it means that instead of the single card having two separate memory interfaces at 1GB each they will run as one interface at 2GB. Should come out soon though.
DirectX11 is the only benefit so far of the ATI 5000 series cards but as with DX10.1 (try finding more than 5 games with DirectX10.1 support) there really is no point. In fact it is said that the change from DX10 to DX11 is about the same as DX9c to DX10: hardly any noticeable difference.
In conclusion:
1) If you can wait then get one or two of the 5000 series cards.
2) If you can't then wait a bit for the 4890X2
3) If you really can't then depeding on resolution either two 4890s or one 4870X2. I would get one 4890, wait for the 4890X2 or 5000 series and Crossfire the 4890 with the newer one you get. That info is based on the fact that the 4870X2 was designed for Crossfire with a single 4870 1GB. The 4890X2 will probably have both cores running as a single thanks to their linked interfaces as I was saying with the 4870X2.
Step 3 is what I would do.
MSI is a great board (
http://www.tomshardware.com/reviews/...-am3,2277.html) especially for multi-GPU CrossfireX configurations. The Phenom 955 is great but make sure you get a good air cooler or liquid cooler as the stock one is crap!
Get some phase change cooling is you want real power. The Phenom 955BE with phase change vs an i7 965 will cost less and will kick the pants off the i7 965 without a sweat; hey, you said money is no object. Let us know how it goes.
More info on 5000 series:
AMD Game Forums - HD 5000 series? Gizmodo - AMD Promises DirectX 11 in 2009 - Graphics
No point in getting anything other than a 5000 series card as your main setup. You can always Crossfire the 4890 with the 5000 series card.
P.S. "One or two cpus of the vid-card?" - I think you mean GPUs dude...