I wouldn't either, as far as a starting setup, but not leaving yourself the single best upgrade option is just blatant stupidity.
Say you were the lucky owner of a 5870 from last generation, but now want more power, which would certainly be reasonable, considering some of the games that are coming out this year like BF3 and Skyrim. Well, jeeze, that fancy GTX 580 sure looks pretty awesome, but $500+?! Oh my, a second 5870 (which is a card with significantly worse CF scaling than current cards) is only $250. I wonder how that compares to a new GTX 580?
http://www.anandtech.com/bench/Product/300?vs=305&i=188.187.191.190.193.194.196.238.199.200.202.203.205.206.208.209.210.212.213.215.216.218.219.228.232.233.231.229.230.234.235
Hehe...yeah, I know why people do it. I had a multi-GPU setup http://en.wikipedia.org/wiki/Voodoo2. See, that's the thing. Depending on your situation it may be a good upgrade option and it may be a lousy one. Bothering with a larger, more expensive motherboard, a larger case with more cooling, and a larger-and-more-expensive-than-needed power supply just to leave you with the option of what usually amounts to a pretty inefficient upgrade in some ways might be a good idea if you're planning on upgrading
next year. Thing is, unless you're driving multiple displays or a
really large one and decided to buy your equipment piecemeal doing yearly upgrades probably means you under-bought on your last card. Planning ahead is not "blatant stupidity," (really not sure why the hostility was necessary there, but whatevz) especially when it's saving you money. If you bought a 5870 at launch and add another for $250 you're talking about $700 in video cards there (in one year) on top of the more expensive mobo and PSU.
Benchmarks are nice and all, buy why shell out for tech that you don't need? My desktop display is 1920x1200 native and my other gaming PC is connected to a TV...so 1920x1080. I don't need a card that can run Crysis at 200fps at 2560×1600 across 3 monitors. I don't need anywhere close to the benchmark numbers those dual 5870's are putting up. So why would I pay for it? I need a card that can run most games maxed-out (or close to it) at 1920x1200 at a decent framerate. Right now I have a 5870, and to be honest there aren't any games right now that make me feel any need to upgrade. By the time I'm ready to upgrade there will be a single-GPU solution that is faster than your 2 x 5870 CF example that costs $350 or less, consumes a similar amount of power and produces a similar amount of heat to a
single 5870, fits in my sixy little Lian-Li mid-tower, doesn't sound like a 747 taking off, doesn't cause SLI/CF oddities in some games, and is utilized 100% by all games whether or not they benefit from AFR or SFR (it's actually pretty surprising how many don't benefit at all). Not only that, but whatever that new GPU is will in all likelihood bring along some new GPU tech along with it.
Like I said, it's a matter of preference. I find that if you buy the right card at the right time you can stay up-to-date by upgrading every 2-3 years to
new tech. I tried to get on the multi-GPU bandwagon several times and I never felt it was worth it to me (except for the dual Voodoo2 cards...
). Some of the instances of SLI/CF becoming a PITA (experienced both first-hand and third) don't endear it to me much either. Others differ, and that's fine...this is
just my opinion after being a gamer that builds their own systems and some for friends and family for...geez...nearly 19 years now. It can be a decent value in some instances, and to be honest I typically do buy multi-video-card-capable boards most of the time for myself these days, but I don't find much use for SLI/CF. Even when I leave the option open it usually doesn't end up to be the best option by the time I'm ready to upgrade.
(You mentioned Skyrim. That's 8 months away. Think about what kind of power you'll be able to get for your dollar in 8 months.)
BTW - incidentally, both of my main PCs'
could support Crossfire, but in both cases the other PCI-E 16x slot is being used by a high-speed storage controller.
Should I consider getting different RAM? That sounds a little outside my range of capabilities unless I take it slow with someone telling me how.
Take a look here:
http://www.ultimatebootcd.com/
If you can burn that CD you'll have a bootable disc with Memtest86+ on it. It's really hard to tell how you're going to fare with a RAM/mobo combination until you try it out (or learn from someone else's experience with the combo). If it's not on the mobo memory compatibility list you're taking your chances, but unfortunately that's usually the case. There are just too many combinations out there to test them all.